In the Old Testament, God commanded Israel to observe several set times of fasting. For New Testament believers, fasting was neither commanded nor forbidden in the Bible. While early Christians were not required to fast, many practiced prayer and fasting regularly. Jesus himself affirmed in Luke 5:35 that after his death fasting would be appropriate for his followers. Spiritual fasting clearly has a place and a purpose for God's people today.
In most cases, a spiritual fast involves abstaining from food while focusing on prayer. This can mean refraining from snacks between meals, skipping one or two meals a day, abstaining only from certain foods, or a total fast from all food for an entire day or longer.
For medical reasons, some people may not be able to fast from food altogether. They may choose to abstain only from certain foods, like sugar or chocolate, or from something other than food. In truth, believers can fast from anything. Doing without something temporarily, such as television or soda, as a way of redirecting our focus from earthly things toward God, can also be considered a spiritual fast.
While many people fast to lose weight, dieting is not the purpose of a spiritual fast. Instead, fasting provides unique spiritual benefits in the life of the believer.
Fasting requires self-control and discipline as one denies the natural desires of the flesh. During spiritual fasting, the believer's focus is removed from the physical things of this world and intensely concentrated on God. Put differently, fasting directs our hunger toward God. It clears the mind and body of earthly attentions and draws us close to God. So, as we gain spiritual clarity of thought while fasting, it allows us to hear God more clearly. Fasting also demonstrates a profound need for God's help and guidance through complete dependence upon him.
The law of Moses specifically required fasting for only one occasion—the Day of Atonement (Leviticus 16:29-30; 23:27-31; Numbers 29:7). This custom resulted in calling this day “the fasting day” (Jeremiah 36:6) or “the fast,” (Acts 27:9). It was a very solemn and holy day with a lot of elaborate ritual. (Leviticus 16; Hebrews 10:1-1). Fasting, however, could also be done for other reasons. It was sometimes done as a sign of distress, grief, or repentance.
Moses did not eat bread or drink water during the 40 days and 40 nights he was on Mount Sinai receiving the law (Exodus 34:28; Deuteronomy 9:9). Jesus fasted 40 days, (Luke 4:2). Elijah fasted 40 days, (1 Kings 19:8). And God's Word has many, many, other fast acts recorded.