Abstinence from all food for a limited period. Rightly motivated fasts were to show godly sorrow and repentance concerning past sins. (1Sa 7:6; Joe 2:12-15; Jon 3:5) They were also fitting in the face of great danger, when in sore need of divine guidance, while enduring tests and meeting temptations, or when studying, meditating, or concentrating on God’s purposes. (2Ch 20:3; Ezr 8:21; Es 4:3, 16; Mt 4:1, 2) Fasting was, not a self-inflicted form of punishment, but a humbling of oneself before Jehovah. (Ezr 8:21; 9:5; compare 1Ki 21:27-29.) Jesus fasted 40 days, as did Moses and Elijah, both of whom appeared in a visionary way with Jesus at his transfiguration.​—Mt 17:1-9; Ex 34:28; De 9:9; 1Ki 19:7, 8.

The Mosaic Law does not use the term “fast,” but in connection with the Day of Atonement it does command, “You must afflict your souls.” (Le 16:29-31; 23:27; Nu 29:7) This is generally understood to mean fasting, and this view is supported by Isaiah 58:3, 5 and Psalm 35:13.

Isaiah chapter 58 deals with a time when the sins of the Jews were heavy; yet they did not sincerely repent, though they made a pretense of worshiping Jehovah, giving him lip service and performing religious acts or practices for show. Fasting was one such practice, and they thought it should gain them divine notice and favor. This failing, they asked in apparent bewilderment: “For what reason did we fast and you did not see, and did we afflict our soul and you would take no note?” Jehovah told them why. Even during the fast, while asking for his righteous judgments and acting as if they carried on righteousness itself, they were pursuing their own pleasure and business, indulging in strife, oppression, and violence; they showed none of the godly sorrow and repentance associated with sincere fasts. Their fast was not such as to make their voice heard in heaven, though their showy wailings were noisy indeed. Jehovah denounced the hypocritical act they put on: “Should the fast that I choose become like this, as a day for earthling man to afflict his soul? For bowing down his head just like a rush, and that he should spread out mere sackcloth and ashes as his couch? Is it this that you call a fast and a day acceptable to Jehovah?”​—Isa 58:1-5.

To be acceptable, the fast must be accompanied by a correction of past sins. Through his prophet Isaiah, Jehovah made known what he considered  to be a real fast, saying: “Is not this the fast that I choose? To loosen the fetters of wickedness, to release the bands of the yoke bar, and to send away the crushed ones free, and that you people should tear in two every yoke bar? Is it not the dividing of your bread out to the hungry one, and that you should bring the afflicted, homeless people into your house? That, in case you should see someone naked, you must cover him, and that you should not hide yourself from your own flesh?”​—Isa 58:6, 7.

Four Annual Fasts of the Jews. The Jews established many fasts, and at one time had four annual ones, evidently to mark the calamitous events associated with Jerusalem’s siege and desolation in the seventh century B.C.E. (Zec 8:19) The four annual fasts were: (1) “The fast of the fourth month” apparently commemorated the breaching of Jerusalem’s walls by the Babylonians on Tammuz 9, 607 B.C.E. (2Ki 25:2-4; Jer 52:5-7) (2) It was in the fifth Jewish month Ab that the temple was destroyed, and evidently “the fast of the fifth month” was held as a reminder of this event. (2Ki 25:8, 9; Jer 52:12, 13) (3) “The fast of the seventh month” was apparently held as a sad remembrance of Gedaliah’s death or of the complete desolation of the land following Gedaliah’s assassination when the remaining Jews, out of fear of the Babylonians, went down into Egypt. (2Ki 25:22-26) (4) “The fast of the tenth month” may have been associated with the exiled Jews already in Babylon receiving the sad news that Jerusalem had fallen (compare Eze 33:21), or it may have commemorated the commencement of Nebuchadnezzar’s successful siege against Jerusalem on the tenth day of that month, in 609 B.C.E.​—2Ki 25:1; Jer 39:1; 52:4.

When certain Jews asked: “Shall I weep in the fifth month, practicing an abstinence, the way I have done these O how many years?” by means of Zechariah, Jehovah answered: “When you fasted . . . for seventy years, did you really fast to me, even me?” God showed that a real fast to him would have been accompanied by obedience and that what he required was truthfulness, judgment, peace, and a sincere heart. Then, instead of fasting mournfully and looking back into the past, they would be able to exult and rejoice in festal seasons with the blessings of restoration of true worship and ingathering of others to Jehovah’s service.​—Zec 7:3-7; 8:16, 19, 23.

Christian Counsel on Fasting. When Jesus was on earth he gave instruction to his disciples: “When you are fasting, stop becoming sad-faced like the hypocrites, for they disfigure their faces that they may appear to men to be fasting. Truly I say to you, They are having their reward in full. But you, when fasting, grease your head and wash your face, that you may appear to be fasting, not to men, but to your Father who is in secrecy; then your Father who is looking on in secrecy will repay you.” (Mt 6:16-18) He alluded here to the insincere fasting of the Pharisees, which he mentioned in an illustration on another occasion. (Lu 18:9-14) It was customary for the Pharisees to fast twice a week, on the second and fifth days of the week.​—Lu 18:12.

A person’s merely abstaining from food in a formalistic manner is described by Paul as subjecting oneself to decrees, “Do not handle, nor taste, nor touch,” and he says that “those very things are, indeed, possessed of an appearance of wisdom in a self-imposed form of worship and mock humility, a severe treatment of the body; but they are of no value in combating the satisfying of the flesh.”​—Col 2:20-23.

Fasting has been enjoined on their members by some religious sects of Christendom, but the Bible itself gives no command to Christians to fast. When Jesus was talking to his disciples about fasting, as above (Mt 6:16-18), he and his disciples were still under the Mosaic Law and observed the Day of Atonement and its fast.

The text about fasting at Matthew 17:21, appearing in the King James Version, is not contained in some of the most important ancient manuscripts. Likewise, although the King James Version mentions fasting at Mark 9:29, Acts 10:30, and 1 Corinthians 7:5, according to such manuscripts these texts do not contain any references to fasting.

Some have taken Matthew 9:15 as a command for Christians to fast. In reality, Jesus was merely making a statement of what was going to happen when he died. While Jesus was with his disciples on earth, it was not appropriate for them to fast. When he died, they did mourn and fast. But they had no cause for mournful fasting after his resurrection and especially after the marvelous outpouring of holy spirit. (Mr 2:18-20; Lu 5:33-35) Certainly Christians were not under obligation to fast on the anniversary of the Lord’s death, for the apostle Paul, correcting abuses in connection with the eating of supper at the congregation’s meeting place before the observance of the Lord’s Evening Meal, said: “Certainly you do have houses for eating and drinking, do you not? . . . Consequently, my brothers, when you come together to eat it [the Lord’s Evening Meal],  wait for one another. If anyone is hungry, let him eat at home, that you may not come together for judgment.”​—1Co 11:22, 33, 34.

While not fasting as a religious requirement, the early Christians did fast on special occasions. When Barnabas and Paul were sent on a special missionary assignment into Asia Minor, there was fasting as well as praying. Also, there was the offering of prayer “with fastings” when elders were appointed in a new congregation. (Ac 13:2, 3; 14:23) Hence, Christians are neither under command to fast nor prohibited from doing so.​—Ro 14:5, 6.