Fasting in Jewish tradition is a religious discipline involving the abstention from food, drink, and physical pleasures, for the purpose of intensifying spiritual experience in atonement for sin, in commemoration of national tragedies, or as part of a personal petition to God in seeking His help.
The best-known example of fasting for the first of the above reasons is the biblical fast of the DAY OF ATONEMENT which is commanded to atone for sin. While fasting is not explicitly mentioned, the Bible ordains for this day "You shall afflict your souls" (Lev. 16:31), and from early times the rabbis interpreted this to mean fasting (Yoma 11a; 73b ff). Part of the "affliction of the soul" also involves a prohibition against bathing, anointing, wearing leather footwear, and engaging in conjugal relations. The gratification of such bodily appetites is seen as a prime source of sin. In Biblical times, rending one's garments and putting on sackcloth and ashes were further signs of distress, accompanying abstention from food (Jonah 3:6ff; Ezek. 9:5). In other cases the fasting is clearly implied (Josh. 7:5-13; Jer. 6:26; Lam. 2:10).
The second category of fasts commemorates tragic events in Jewish history. These are, first of all, the four historical fasts mentioned in the Bible: 10 Tevet, 17 Tammuz , 9 Av, and 3 Tishri (the Fast of GEDALIAH). All of them are connected with the sieges of Jerusalem and the destruction of the First and Second Temples. The post-exilic prophet Zechariah prophesied that in the future period of national redemption these four historical fasts would be changed to days of gladness and joy (Zech. 8:19).
With the exception of Tishah Beh’av these historical fasts are usually described as "minor." Two halakhic stipulations emphasize this distinction. First, the fast begins at dawn on the day itself and not at sunset on the previous evening as is the case with the Day of Atonement and Tishah be-Av. Secondly, the additional four prohibitions (bathing, anointing, leather shoes, and sexual relations) are not added to the prohibition against eating and drinking as on the Day of Atonement and Tishah be-Av.
The Bible records other instances of fasting with sackcloth and ashes at times of national crises. Thus, after the defeat at Ai (Josh. 7:5- 13) and in the tribal war against Benjamin (Judg. 20:23-26), the leaders of the time proclaimed a fast.
The third category of fasting, the fast of petition, is illustrated by Esther's call to her fellow Jews to observe a three-day fast as she prepared to plead with the king for her people (Esther 4:16-17). The fast of petition is represented in enactments by the rabbis proclaiming fasts in times of national danger. Just as in Bible times the leaders called the people to a fast and a special assembly (Joel 2: 14), so in the rabbinic tradition fast days were called by the rabbis when the people were exhorted to fast and pray for God's help in times of severe drought or plague (Ta'an. 3:5-8). An entire tractate of the Talmud, viz., Ta'anit (Fast) is devoted to the subject.
Various rabbinic laws are associated with fasting. The obligatory fasts have to be observed by all males over the age of 13 and females over the age of 12. In order to train the religious loyalty and self- discipline of younger people, the rabbis encouraged youngsters below those ages to observe partial fasts.
