We have already discussed the curious fact that the book of Esther does not mention God, nor anything explicitly religious. However, we are told that Esther, Mordecai, and the other Jews all fasted (Esth 4:3,16). Since we can be fairly confident that they were not simply trying to lose weight, we can assume that this fasting was accompanied by prayer for God’s deliverance. (Fasting was also associated with mourning someone’s death, but surely the Jews had not yet given up hope of being saved at this point).
As far as I am aware, there are no general commands to fast in the Bible (although it appears the Jews did have certain fasts they observed – e.g. Zech 8:19; Acts 27:9). There is no specified amount of fasting that ought to be done, or special dates on which you ought to fast. However, there are many calls to fast, especially in the Old Testament. These usually happen at times of national crisis, and as people fast together they express their desperation for God to act.
Fasting seems to be associated with devoting yourself to calling on God for a specific reason at a crucial time. John Piper interprets the meaning of fasting as expressing a deep hunger for God – as we fast we effectively say “I need you more than I need food”. He calls it a “homesickness for God”.
Jesus indicates that he anticipated that his followers would sometimes fast (Matt 6:16-18; 9:15), but does not specify when. I suspect that it is assumed that the pattern of leaders calling fasts would continue (e.g. Acts 13:2,3). Also, individuals or smaller groups will find on occasions that they feel the need to devote themselves to serious seeking after God in prayer at significant moments in their lives.
It is surely notable that in a book full of feasting, God’s people are found fasting at the point where humanly speaking, there seemed to be no hope. Whilst feasting is a great way to express our gratitude to God, fasting still has a place to express our utter dependence on him. If we find that we rarely or never fast, does that suggest a self-sufficiency on our part? Is it indicative of a lack of genuine hunger for God?