When I was a young Protestant and much opposed to any form of penance (“Hey, Jesus forgave our sins! Why do we need to do penance?”), my Episcopalian aunt pointed my attention to the Sermon on the Mount, where Jesus says: “And when you fast, do not look dismal, like the hypocrites, for they disfigure their faces that their fasting may be seen by men. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by men but by your Father who is in secret; and your Father who sees in secret will reward you” (Matt. 6:16–18; cf. Mark 2:18–20).
My aunt stressed that Jesus said “when you fast” not “if you fast.” He expected his followers to fast, so it is no surprise that we find them doing so: “While they were worshiping the Lord and fasting, the Holy Spirit said, ‘Set apart for me Barnabas and Saul for the work to which I have called them.’ So after they had fasted and prayed, they placed their hands on them and sent them off” (Acts 13:2–3; cf. 14:23). The question is not “Should Christians fast?” but “Why should Christians fast—what are we trying to accomplish by it?”
As a Protestant I heard that one should fast so he can spend in prayer the time he otherwise would spend eating. It’s easy to see why a Protestant would choose this explanation (it strips fasting of any penitential connotation), but it doesn’t work.
One can pray while eating, or one can eat quickly and spend the rest of the allotted meal time praying. To get still more time for prayer, one could make other cuts in the day’s schedule—cuts that produce less discomfort than does fasting. Either of these options—eating quickly or cutting other parts of one’s schedule—avoid the hunger pains that fasting produces.
If the goal were merely to get more time for prayer, avoiding hunger would be important. The average person does not pray well if he is ravenously hungry. By dinner time, having skipped breakfast and lunch, he will be distracted by hunger. That could cause him to pray less effectively than if he had eaten and then devoted himself to prayer.
An alternative justification for fasting is that it purifies one physically. While fasting may have beneficial physical effects, such as removing toxins from the body, this cannot be the underlying explanation for the Christian practice. To get significant physical effects from fasting, one would have to do precisely the right amount of it. A one-day fast does little for one’s body, and a prolonged fast will harm it, and the Bible gives no regulations about how long one should fast. More fundamentally, Jesus does not ask us to fast so that we can benefit physically. He is not recommending it as a diet or health-improvement technique. He intends it to do something spiritual.
Fasting (and embracing the hunger that it produces) improves us spiritually in several ways: We express our recognition that spiritual things are more important than physical things. We learn to deny ourselves pleasures, even in spite of pain—an important spiritual lesson. We declare that we recognize the need to reform and to get closer to God. We willingly embrace the hunger fasting produces as a sign of being willing to shoulder the burdens of others (cf. Col. 1:24). Finally, we express humility before God by adopting a humble posture, recognizing our dependence on him and affirming our submissiveness to his will.
This posture of humility is linked with fasting in Scripture. The scribe Ezra tells us, “Then I proclaimed a fast . . . that we might humble ourselves before our God, to seek from him a straight way for ourselves, our children, and all our goods” (Ezra 8:21). These spiritual effects—and the consequently more effective prayer life that greater spirituality brings (Jas. 5:16b)—are the reason Jesus not only approves of fasting, but expects his followers to fast.
Fasting does relate to prayer and is used in the Bible as a way of petitioning God. But the humility one expresses in fasting must be real and not affected. God castigates those who fast but do not truly repent: “[O]n the day of your fasting, you do as you please and exploit all your workers. Your fasting ends in quarreling and strife, and in striking each other with wicked fists. You cannot fast as you do today and expect your voice to be heard on high” (Is. 58:3b-4).