The soul is independent of any sickness or disability of body or mind

Know thou that the soul of man is exalted above, and is independent of all infirmities of body or mind. That a sick person showeth signs of weakness is due to the hindrances that interpose themselves between his soul and his body, for the soul itself remaineth unaffected by any bodily ailments. Consider the light of the lamp. Though an external object may interfere with its radiance, the light itself continueth to shine with undiminished power. In like manner, every malady afflicting the body of man is an impediment that preventeth the soul from manifesting its inherent might and power. When it leaveth the body, however, it will evince such ascendancy, and reveal such influence as no force on earth can equal. Every pure, every refined and sanctified soul will be endowed with tremendous power, and shall rejoice with exceeding gladness. 

- Baha’u’llah  (‘Gleanings from the Writings of Bahá'u'lláh’)

The “human spirit, unless assisted by the spirit of faith, does not become acquainted with the divine secrets and the heavenly realities.”

It has been before explained that spirit is universally divided into five categories: the vegetable spirit, the animal spirit, the human spirit, the spirit of faith, and the Holy Spirit.

The vegetable spirit is the power of growth which is brought about in the seed through the influence of other existences.

The animal spirit is the power of all the senses, which is realized from the composition and mingling of elements; when this composition decomposes, the power also perishes and becomes annihilated. It may be likened to this lamp: when the oil, wick, and fire are combined it is lighted, and when this combination is dissolved, that is to say, when the combined parts are separated from one another, the lamp also is extinguished.

The human spirit which distinguishes man from the animal is the rational soul; and these two names—the human spirit and the rational soul—designate one thing. This spirit, which in the terminology of the philosophers is the rational soul, embraces all beings, and as far as human ability permits discovers the realities of things and becomes cognizant of their peculiarities and effects, and of the qualities and properties of beings. But the human spirit, unless assisted by the spirit of faith, does not become acquainted with the divine secrets and the heavenly realities. It is like a mirror which, although clear, polished, and brilliant, is still in need of light. Until a ray of the sun reflects upon it, it cannot discover the heavenly secrets.

But the mind is the power of the human spirit. Spirit is the lamp; mind is the light which shines from the lamp. Spirit is the tree, and the mind is the fruit. Mind is the perfection of the spirit, and is its essential quality, as the sun’s rays are the essential necessity of the sun. 

- ‘Abdu’l-Baha  (‘The Baha’i World Faith’)

“…spirit in general is divided into five sorts—the vegetable spirit, the animal spirit, the human spirit, the spirit of faith, and the divine spirit of sanctity.”

Now as to what thou askest concerning the spirit and its “return” to this world of humanity and this elemental space: Know that spirit in general is divided into five sorts—the vegetable spirit, the animal spirit, the human spirit, the spirit of faith, and the divine spirit of sanctity.

The vegetable spirit is the virtue augmentative, or growing or vegetative faculty, which results from the admixture of the simple elements, with the co-operation of water, air and heat.

The animal spirit is the virtue perceptive resulting from the admixture and absorption of the vital elements generated in the heart, which apprehend sense impressions.

The human spirit consists of the rational, or logical, reasoning faculty, which apprehends general ideas and things intelligible and perceptible.

Now these “spirits” are not reckoned as Spirit in the terminology of the Scriptures and the usage of the people of the Truth, inasmuch as the laws governing them are as the laws which govern all phenomenal being (i.e., all existences belonging to the phenomenal or material universe, called “the world of generation and corruption”), in respect to generation, corruption, production, change and reversion, as is clearly indicated in the Gospel where it says: “Let the dead bury their dead;” “That which is born of the flesh is flesh, and that which is born of the Spirit is Spirit”; inasmuch as he who would bury these dead was alive with the vegetative, animal and rational human soul, yet did Christ—to whom be glory! — declare such dead and devoid of life, in that this person was devoid of the Spirit of Faith, which is of the Kingdom of God. 

- ‘Abdu’l-Baha  (‘Tablets of ‘Abdu’l-Baha’, vol. 1)

One’s consciousness after death in relation to others

….the soul after its separation from the body keeps its individuality and its consciousness both in relation to other souls and to the human beings in this world. 

- Shoghi Effendi  (From a letter dated 26 November 1939 written on behalf of Shoghi Effendi to an individual believer; compilation ‘Reincarnation and the Nature and Progress of the Soul’, prepared by the Research Department of the Universal House of Justice)

Man’s identity after death

Man’s identity or rather his individuality is never lost. His reality as a person remains intact throughout the various stages of his development. He does not pre-exist in any form before coming into this world.... 

- Shoghi Effendi  (From a letter dated 26 November 1939 written on behalf of Shoghi Effendi to an individual believer; compilation ‘Reincarnation and the Nature and Progress of the Soul’, prepared by the Research Department of the Universal House of Justice)

Human evolution “continues after death”

Evolution in the life of the individual starts with the formation of the human embryo and passes through various stages, and even continues after death in another form. The human spirit is capable of infinite development. 

- Shoghi Effendi  (From a letter dated 26 November 1939 written on behalf of Shoghi Effendi to an individual believer; compilation ‘Reincarnation and the Nature and Progress of the Soul’, prepared by the Research Department of the Universal House of Justice)

At the time of separation from the body the soul “is gladdened by goodly deeds and profiteth from the contributions made in the path of God"

The sixth question: “After relinquishing the body, that is to say, after the soul hath been separated from the body, it hasteneth to the abode hereafter….”

In reference to this theme there appeared some time past from the Pen of divine knowledge that which sufficeth the men of insight and imparteth the greatest joy to the people of understanding. Verily, We say: The soul is gladdened by goodly deeds and profiteth from the contributions made in the path of God. 

- Baha’u’llah  (‘The Tabernacle of Unity, Bahá’u’lláh’s Responses to Mánikchí Sáhib and Other Writings’)

“The human reality in the other world has… the likeness of the Kingdom”

The human reality in the other world has no physical likeness, nay, rather, it has the likeness of the Kingdom, which consists of the harmonious element of the realm of the Spiritual Kingdom. 

- ‘Abdu’l-Baha  (From a Tablet, Star of the West, vol. 2, no. 5, June 5, 1911)

No “trials” in the next world

The Divine trials are in this world not in the world of the Kingdom. 

- ‘Abdu’l-Baha  (From a Tablet, Star of the West, vol. 2, no. 5, June 5, 1911)

There are various “grades” of existence in the next world as we similarly have in this world – such as the mineral, vegetable, animal, and human

The spirits of the sons of the Kingdom after the disintegration of this body ascend to the world of Eternal Existence; but should you ask of the place, know thou that that world of existence is the world of unity, but the grades are different. For instance, the mineral existence has a grade, but that mineral being has no knowledge of the vegetable kingdom. It (the mineral existence) has no information of a higher realm nay, rather, according to appearances, it may deny the higher grade. Likewise the vegetable life has no knowledge of the animal kingdom. It is entirely heedless and unconscious of that kingdom, because the grade of the animal is higher than that of the vegetable. The vegetable, according to its limited environment, is veiled from the knowledge of the animal kingdom, and it may deny it, although the animal, the vegetable and mineral live in the world of existence. Likewise, the animal cannot comprehend the intelligence of the faculties of man, which is the generalizer of the universal and the discoverer of the mysteries of beings, so much so that while living in the East he organizes and founds institutions in the West, and he reveals hidden things. Though he abides in Europe he discovers America. Though he dwells upon the earth, he unravels the realities of the solar system. The animal is entirely unconscious, nay, rather, a denier of this intelligent force, which penetrates into the unknown and comprehends the general as well as the particular ideas of this illimitable universe.

Condition of souls in the next world

Mrs. S. asked some questions with reference to the conditions of existence in the next world, and the life after death; she said that having recently lost a very near relative, she had given much thought to this subject. Many thought that re-union with those we had loved, and who had passed on to the future life, would only take place after a long period of time had elapsed. She wished to know whether one would be re-united with those who had gone before immediately after death.

'Abdu'l-Bahá answered that this would depend upon the respective stations of the two. If both had the same degree of development, they would be re-united immediately after death.

The questioner then said, how could this state of development be acquired?

'Abdu'l-Bahá replied, by unceasing effort, striving to do right, and to attain spiritual qualities.

The questioner remarked that many differing opinions were held as to the conditions of the future life. Some thought that all would have exactly the same perfections and virtues; that all would be equal and alike.

'Abdu'l-Bahá said there would be variety, and differing degrees of attainment, as in this world.

It is one’s “inner temple” that “takes delight in joy or is saddened by pain”

As this physical frame is the throne of the inner temple, whatever occurs to the former is felt by the latter. In reality that which takes delight in joy or is saddened by pain is the inner temple of the body, not the body itself. Since this physical body is the throne whereon the inner temple is established, God hath ordained that the body be preserved to the extent possible, so that nothing that causeth repugnance may be experienced. The inner temple beholdeth its physical frame, which is its throne. Thus, if the latter is accorded respect, it is as if the former is the recipient. The converse is likewise true.

Therefore, it hath been ordained that the dead body should be treated with the utmost honour and respect. 

- The Báb  (Selections from the Writings of the Báb)

When the soul leaves the body…

When the human soul soareth out of this transient heap of dust and riseth into the world of God, then veils will fall away, and verities will come to light, and all things unknown before will be made clear, and hidden truths be understood

- ‘Abdu'l-Baha  (Selections from the Writings of 'Abdu'l-Baha)

The body draws its sustenance from the soul

The soul of man is the sun by which his body is illumined, and from which it draweth its sustenance… 

- Baha'u'llah  (‘Gleanings from the Writings of Baha'u'llah’)

The “soul retains its individuality and consciousness after death”

...The possibility of securing union with his beloved in the next world is one which the Bahá'í Teachings are quite clear about. According to Bahá'u'lláh the soul retains its individuality and consciousness after death, and is able to commune with other souls. This communion, however, is purely spiritual in character, and is conditioned upon the disinterested and selfless love of the individuals for each other. 

- Shoghi Effendi (From a letter written on behalf of Shoghi Effendi to the National Spiritual Assembly of India, March 10, 1936: ‘Dawn of a New Day’; compilation: ‘Lights of Guidance’)

The station of a believer’s non-Baha’i parents in the next world

Thou hast mentioned the station of parents in the next world. One of the special bounties of this Revelation is that whoever accepteth the Dayspring of the Cause, his parents, although they may not have attained the recognition of the Revelation, the splendours of the Sun of divine favor will be vouchsafed unto them. This is one of His bounties bestowed upon His lovers. Render thanks and be of those who are grateful. 

- Baha’u’llah  (Quoted in a Memorandum from the Research Department of the Universal House of Justice, dated 28 August 1991)

The condition of non-Baha’i relatives after death -- explanation by the Research Department of the Universal House of Justice

The Research Department has studied the questions about the spiritual condition of souls of the non-Baha'i relatives of Baha'is, which were contained in the letter dated 26 July 1991 from Mr…. to the Universal House of Justice. Mr…. cites the following extract from a Tablet revealed by Baha'u'llah and raises a number of issues about its meaning and application:

These blessed words were uttered by the Tongue of Grandeur in the Land of Mystery, [Adrianople] exalted and glorified is His utterance: 

One of the distinguishing characteristics of this most great Dispensation is that the kin of such as have recognized and embraced the truth of this Revelation and have, in the glory of His name, the Sovereign Lord, quaffed the choice, sealed wine from the chalice of the love of the one true God, will, upon their death, if they are outwardly non-believers, be graciously invested with divine forgiveness and partake of the ocean of His mercy.

This bounty, however, will be vouchsafed only to such souls as have inflicted no harm upon Him Who is the Sovereign Truth nor upon His loved ones. Thus hath it been ordained by Him Who is the Lord of the Throne on High and the Ruler of this world and the world to come. (Baha’u’llah, The Compilation of Compilations, vol. 1, Family)

“…soul is as the sun, and... mental faculties even as the rays that emanate from that source of light.”

…regarding the question whether the faculties of the mind and the human soul are one and the same. These faculties are but the inherent properties of the soul, such as the power of imagination, of thought, of understanding; powers that are the essential requisites of the reality of man, even as the solar ray is the inherent property of the sun. The temple of man is like unto a mirror, his soul is as the sun, and his mental faculties even as the rays that emanate from that source of light. The ray may cease to fall upon the mirror, but it can in no wise be dissociated from the sun. 

(‘Abdu’l-Baha, ’Tablet to August Forel’)

The “spiritual world” and the “phenomenal world” are the “exact counterpart of each other”

The spiritual world is like unto the phenomenal world. They are the exact counterpart of each other. Whatever objects appear in this world of existence are the outer pictures of the world of heaven.

(‘Abdu’l-Baha, from a talk, 13 April 1912, New York; ‘The Promulgation of Universal Peace’)

Human “soul is endowed with two wings”

Know also that the soul is endowed with two wings: should it soar in the atmosphere of love and contentment, then it will be related to the All-Merciful. And should it fly in the atmosphere of self and desire, then it will pertain to the Evil One; may God shield and protect us and protect you therefrom, O ye who perceive! Should the soul become ignited with the fire of the love of God, it is called benevolent and pleasing unto God, but should it be consumed with the fire of passion, it is known as the concupiscent soul. Thus have We expounded this subject for thee that thou mayest obtain a clear understanding. 
(Baha'u'llah, Súriy-i-Ra’ís, ‘The Summons of the Lord of Hosts’)

What things should a human soul attach itself to?

Happy is the pure soul who does not attach himself to transient conditions and comforts, but rather seeks to attach himself to the purity, nobility and splendor of the world which endures. 
(‘Abdu’l-Baha, Baha'i Scriptures; Star of the West, vol. IV, No. 16, December 31, 1913)

Meaning of the term “soul” in various kingdoms of creation -- 'Abdu'l-Baha explains

As to the question concerning the soul, know thou, verily, that "soul" is a term applied to numerous realities, according to the exigencies of the following relations in regard to development in the world of existence:

(1) In the mineral kingdom, soul is called "latent force," silently working for the disintegration of the substance of the mineral.

(2) In the vegetable kingdom it is called “virtue augmentative," or the power of growth, which attracts and absorbs the delicate materials of inorganic substance found in the mineral kingdom of matter, and transforms them into the condition of growth. Thus the inorganic substance found in the mineral kingdom becomes growing vegetable life through the effect of the word of God. This vegetable soul, i. e. "virtue augmentative," or power of growth, is a quality which is produced by the admixture of elements, and appears in accidental organisms, of which contingency is an essential attribute.

Prayer is the “spiritual nourishment” for the human soul

It is the soul of man that has first to be fed. And this spiritual nourishment prayer can best provide. Laws and institutions, as viewed by Bahá'u'lláh, can become really effective only when our inner spiritual life has been perfected and transformed. Otherwise religion will degenerate into a mere organization, and become a dead thing. 
(From a letter dated 8 December 1935 written on behalf of Shoghi Effendi to an individual believer, published in "Bahá'í News" 102 (August 1936), p. 3; The Compilation of Compilations, Vol. II, The Importance of Prayer, Meditation and the Devotional Attitude)

The “body is dependent upon the soul”

Furthermore, many say, `We have no need of divine Manifestations; we ourselves have direct communication with God.' They do not know that the divine Manifestations are the bright rays of the Sun of Truth and a means of educating the realities of man. Therefore, he who rejects the bounty of the Sun of Truth and thinks himself not in need of it is like the one who says he is not in need of God and rejects both God and reality, in spite of the fact that all creation is receiving incessant bounty from God and is dependent on Him, as the body is dependent upon the soul. 
(Words of ‘Abdu’l-Baha, New York, November 26, 1912, Mahmud’s Diary)

“…greed and envy becloudeth the radiance of the soul even as the clouds obstruct the light of the sun.”

O children of understanding! If the eyelid, however delicate, can deprive man’s outer eye from beholding the world and all that is therein, consider then what would be wrought if the veil of covetousness were to descend upon his inner eye. Say: O people! The darkness of greed and envy becloudeth the radiance of the soul even as the clouds obstruct the light of the sun. Should anyone hearken unto this utterance with a discerning ear, he will unfurl the wings of detachment and soar effortlessly in the atmosphere of true understanding. 
(Baha’u’llah, ‘The Tabernacle of Unity, Bahá’u’lláh’s Responses to Mánikchí Sáhib and Other Writings’)