One fast only was appointed by the Mosaic law, that on the day of atonement. There is no mention of any other periodical fast in the Old Testament except in (Zechariah 7:1-7; 8:19) From these passages it appears that the Jews, during their captivity, observed four annual fasts,-in the fourth, fifth, seventh and tenth months.
• Public fasts were occasionally proclaimed to express national humiliation and to supplicate divine favor. In the case of public danger the proclamation appears to have been accompanied with the blowing of trumpets. (Joel 2:1-15) (See (1 Samuel 7:6; 2 Chronicles 20:3; Jeremiah 36:6-10))
Three days after the feast of tabernacles, when the second temple was completed, "the children of Israel assembled with fasting, and with sackclothes and earth upon them," to hear the law read and to confess their sins. (Nehemiah 9:1)
• Private occasional fasts are recognized in one passage of the law- (Numbers 30:13) The instances given of individuals fasting under the influence of grief, vexation or anxiety are numerous.
• In the New Testament the only reference to the Jewish fasts are the mention of "the fast" in (Acts 27:9) (generally understood to denote the day of atonement) an the allusions to the weekly fasts. (Matthew 9:14; Mark 2:18; Luke 5:33; 18:12; Acts 10:30) These fasts originated some time after the captivity.
• The Jewish fasts were observed with various degrees of strictness. Sometimes there was entire abstinence from food. (Esther 4:16) etc. On other occasions there appears to have been only a restriction to a very plain diet. (Daniel 10:3) Those who fasted frequently dressed in sackcloth or rent their clothes, put ashes on their head and went barefoot. (1 Kings 21:27; Nehemiah 9:1; Psalms 35:13)
• The sacrifice of the personal will, which gives to fasting all its value, is expressed in the old term used in the law, afflicting the soul .