Answer: The Divine wisdom in fasting is manifold. Among them is this: As during those days (i.e. the period of fasting which the followers afterward observe) the Manifestation of the Sun of Reality, through Divine inspiration, is engaged in the Descent of Verses, the instituting of Divine Law and the arrangement of Teachings, through excessive occupation and intense attraction there remains no condition or time for eating and drinking. For example, when His Holiness Moses went to Mount Tur (Sinai) and there engaged in instituting the Law of God, he fasted forty days. For the purpose of awakening and admonishing the people of Israel, fasting was enjoined upon them.
Likewise His Holiness Christ in the beginning of instituting the Spiritual Law, the systematizing of the Teachings and the arrangement of counsels, for forty days abstained from eating and drinking. In the beginning the disciples and Christians fasted. Later the assemblages of the chief Christians changed fasting into Lenten observances.
Likewise the Koran having descended in the month Ramazan, fasting during that month became a duty. In like manner His Holiness the Supreme (the BAB), in the beginning of the Manifestation, through the excessive effect of descending Verses, passed days in which his nourishment was reduced to tea only.
Likewise, the Blessed Beauty (BAHA'U'LLAH), when busy with instituting the Divine Teachings and during the days when the Verses (the Word of God) descended continuously through the great effect of the Verses and the throbbing of the heart, took no food except the least amount.
The purpose is this: In order to follow the Divine Manifestations and for the purpose of admonition and the commemoration of their state, it became incumbent upon the people to fast during those days.
The Christians, as was written, formerly fasted fully. For every sincere soul who has a beloved longs to experience that state in which his beloved is. If his beloved is in a state of sorrow, he desires sorrow; if in a state of joy he desires joy; if in a state of rest, he desires rest; if in a state of trouble, he desires trouble.
Now since in those days His Holiness the Supreme (the BAB) fasted many days, and the Blessed Beauty (BAHA'U'LLAH) took but little food or drink, and some days Christ did not eat, it became necessary that the friends should follow that example. For thus saith He in the Tablet of Visitation: "They, the believers, have followed that which they were commanded, for love of Thee." This is one wisdom of the wisdoms of fasting.
The second wisdom is this: Fasting is the cause of awakening man. The heart becomes tender and the spirituality of man increases. This is produced by the fact that man's thoughts will be confined to the commemoration of God, and through this awakening and stimulation surely ideal advancements follow.
Third wisdom: Fasting is of two kinds, material and spiritual. The material fasting is abstaining from food or drink, that is, from the appetites of the body. But spiritual, ideal fasting is this, that man abstain from selfish passions, from negligence and from satanic animal traits. Therefore material fasting is a token of the spiritual fasting. That is: O God! as I am fasting from the appetites of the body and not occupied with eating and drinking, even so purify and make holy my heart and my life from aught else save Thy Love, and protect and preserve my soul from self-passions and animal traits. Thus may the spirit associate with the Fragrances of Holiness and fast from everything else save Thy mention. (‘Abdu’l-Baha, notes of a table talk in Akka in 1907; Corine True, ‘Notes Taken at Acca’, booklet published by Baha’i Publishing Society, Chicago 1907)