Although ill health is one of the unavoidable conditions of man, truly it is hard to bear. The bounty of good health is the greatest of gifts.
(‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, p.151)

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.
(The Báb)

Issues of food, nutrition, health and shelter are central to the challenge of providing an adequate standard of living for all members of the human family. ...While individuals must do their utmost to provide for themselves and their dependents, the community must accept responsibility, when necessary, to help meet basic needs.
(Bahá’í International Community, February 18, 1998, “Valuing Spirituality in Development")

It must be acknowledged, however, that some illnesses reflect unwholesome human behavior. The inclusion of moral development in education would, therefore, help to reduce significantly certain current health problems.
(Bahá’í International Community, February 18, 1998, “Valuing Spirituality in Development")

Knowledge of human conditions and the needed remedy for them is not the cause of their betterment. To admit that health is good does not constitute health. A skilled physician is needed to remedy existing human conditions. As a physician is required to have complete knowledge of pathology, diagnosis, therapeutics and treatment, so this World Physician must be wise, skillful and capable before health will result. His mere knowledge is not health; it must be applied and the remedy carried out.
(‘Abdu’l-Bahá, Foundations of World Unity, p. 100)

Looking after one’s health is done with two intentions. Man may take good care of his body for the purpose of satisfying his personal wishes. Or, he may look after his health with the good intention of serving humanity and of living long enough to perform his duty toward mankind. The latter is more commendable. Between material things and spiritual things there is a connection. The more healthful his body the greater will be the power of the spirit of man; the power of the intellect, the power of the memory, the power of reflection will be greater.
(‘Abdu’l-Bahá, Star of the West, Vol VIII, No. 18, p. 231)

Make ye then a mighty effort, that the purity and sanctity which, above all else, are cherished by ?bdu’l-Bahá, shall distinguish the people of Bahá; that in every kind of excellence the people of God shall surpass all other human beings; that both outwardly and inwardly they shall prove superior to the rest; that for purity, immaculacy, refinement, and the preservation of health, they shall be leaders in the vanguard of those who know. And that by their freedom from enslavement, their knowledge, their self-control, they shall be first among the pure, the free and the wise.
(?bdu’l-Bahá, Selections from the Writings of ?bdu’l-Bahá, p. 150)

Now your father has taken you to the best nerve specialists in..., and they all recommend that you should suspend all your activities until you are fully recovered. It is now your duty as a Bahá’í, and specially as a young believer who has still great services to render the Faith, to make every effort to recovery your health, and to be confident that by making such an effort you will be attracting the confirmations of Bahá’u’lláh, without which no true and lasting healing is possible.
(Shoghi Effendi, Lights of Guidance, p. 292)

Our appetites and inclinations are strongly influenced by the condition of our physical makeup, and our bodies are in varying degrees of health, depending upon factors such as heredity, environment, nourishment and our own treatment of them. Genetic variations occur, producing conditions which can create problems for the individual. Some conditions are of an emotional or psychological nature, producing such imbalances as quickness to anger, recklessness, timorousness, and so forth; others involve purely physical characteristics, resulting not only in unusual capacities but also in handicaps or diseases of various kinds.
(Universal House of Justice, September 11, 1995, to a National Spiritual Assembly)

The physical, mental and spiritual health of the Bahá’í community has a bearing on its ability to function effectively, attract the wider community, retain and support an active membership.
(USA-NSA, Guidelines for Local Spiritual Assemblies, p. 3)

Whether deficiencies are inborn or are acquired, our purpose in this life is to overcome them and to train ourselves in accordance with the pattern that is revealed to us in the divine Teachings.
(Universal House of Justice, September 11, 1995, to a National Spiritual Assembly)

With regard to health — the physical, spiritual, mental and social well-being of the individual — access to clean water, shelter, and some form of cheap energy would go a long way toward eradicating the problems that currently plague vast numbers of individuals and communities.
(Bahá’í International Community, February 18, 1998, “Valuing Spirituality in Development")

You should always bear in mind Bahá’u’lláh’s counsel that we should take the utmost care of our health, surely not because it is an end in itself, but as a necessary means of serving His Cause. In case of illness, He emphatically tells us, we should refer to the most competent physicians.
(Shoghi Effendi, Lights of Guidance, p. 291-292)

You should not neglect your health, but consider it the means which enables you to serve. It—the body—is like a horse which carries the personality and spirit, and as such should be well cared for so it can do its work! You should certainly safeguard your nerves, and force yourself to take time, and not only for prayer meditation, but for real rest and relaxation.
(Shoghi Effendi, Lights of Guidance, p. 296)