Fasting is a biblical practice, but it’s biblical in a peculiar way.
It’s presupposed on page after page, but never explained. “When you fast” is a typical beginning for a biblical sentence on the subject, and it leads modern readers to wonder if we missed a page somewhere back in the Old Testament —maybe in Leviticus?— that established the whole idea of fasting to begin with. But no, Kent Berghuis did a dissertation that studied every biblical reference to abstaining from food, and from the very first reference to fasting in the Old Testament, it just presupposes that the practice is well known and that we’ll understand what it’s for. Fasting is, after all, pretty much universal in world religions. Just about anywhere you find religion, you find fasting. Perhaps that’s why the authors of the Bible take it for granted.
As a result, what we have in fasting is a practice presupposed by the Bible but not directly established. “When you fast” —not if you fast, or “here’s an idea you never thought of: fast.” It’s a kind of biblical extra-biblical religious practice.
And then, to make matters weirder, the most detailed passages about fasting are negative, corrective, and even sarcastic. God’s best lecture on fasting comes in Isaiah 58:3-6 when the Israelites complain “Why have we fasted, and you see it not?” God responds, “Because you’re fasting wrong!” He’s not upset with their ascetical technique or their liturgical schedule, but with their lack of justice and their self-righteousness:
Is not this the fast that I choose:
to loose the bonds of wickedness,
to undo the straps of the yoke,
to let the oppressed go free,
and to break every yoke?
The basic idea of the passage is something like, “You call that a fast? I’ve got an idea: why don’t you try fasting from wickedness?”
And in the New Testament (Matthew 6:16-18), Jesus gives some clear directions about fasting in a similarly negative mode:
And when you fast, do not look gloomy like the hypocrites, for they disfigure their faces that their fasting may be seen by others. 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 others but by your Father who is in secret. And your Father who sees in secret will reward you.
Taken together with Paul’s warnings about the dangers of cultic scrupulosity over food and ritual practices (Col. 2:16-19), it’s enough to make you think that the Bible’s main interest in fasting is to warn us about its spiritual danger! And church history provides its share of abuses of the practice, perhaps the most striking being the arrest of Swiss printers for eating sausage during Lent in 1522 so they could have strength to print Bibles. That was a situation that needed some Reforming, and Zwingli provided it.
But abuses don’t rule out proper uses, and throwing out fasting altogether would be a big mistake —an unbiblical move. While it’s true that the most detailed information about fasting comes obliquely and ironically through warning passages, we should also pay attention to how widespread the casual references to it are. If you dig into those and think about the presuppositions behind them, you can catch a glimpse of the purposes and results of fasting. Wayne Grudem summarizes some of the obvious ones handily in Chapter 18 of his Systematic Theology: An Introduction to Biblical Doctrine:
1. It increases our sense of humility and dependence on God.
2. It allows us to give more attention to prayer.
3. It reminds us that we need to sacrifice all of ourselves to God.
4. It is good exercise in self-discipline and restraint.
5. It heightens spiritual and mental awareness and a sense of God’s presence.
6. It expresses earnestness and urgency in our prayers.
John Calvin’s summary statement of the goals of fasting is helpful: “A holy and lawful fast has three ends in view. We use it either to mortify and subdue the flesh, that it may not wanton, or to prepare the better for prayer and holy meditation; or to give evidence of humbling ourselves before God, when we would confess our guilt before him.” (from his Institutes, Book IV, Chapter 12, section 15)
There is an ancient Christian tradition of fasting in preparation for Easter. Whether you’re among The Liturgically Correct who started the observance of Lent with Ash Wednesday last week, or whether your church is less engaged with a traditional church seasonal calendar, the basic idea of doing some deep preparation for Good Friday and Easter comes from a solid Christian instinct: the death and resurrection of Christ are, together, the one main event of Christianity. That makes the weeks before Easter a good time to consider the biblical practice of fasting. John Piper has a Piper-perfect book on it that you can read for free, and bible.org has some great background information.
Andrew Murray’s chapter on the subject in With Christ in the School of Prayer includes this wise observation:
And prayer needs fasting for its full growth… Prayer is the one hand with which we grasp the invisible; fasting, the other, with which we let loose and cast away the visible. […] Prayer is the reaching out after God and the unseen; fasting, the letting go of all that is of the seen and temporal. While ordinary Christians imagine that all that is not positively forbidden and sinful is lawful to them, and seek to retain as much as possible of this world, with its property, its literature, its enjoyments, the truly consecrated soul is as the soldier who carries only what he needs for the warfare. Laying aside every weight, as well as the easily besetting sin, afraid of entangling himself with the affairs of this life, he seeks to lead a Nazarite life, as one specially set apart for the Lord and His service. Without such voluntary separation, even from what is lawful, no one will attain power in prayer: this kind goeth not out but by fasting and prayer.
Disciples of Jesus! who have asked the Master to teach you to pray, come now and accept His lessons. He tells you that prayer is the path to faith, strong faith, that can cast out devils. He tells you: ‘If ye have faith, nothing shall be impossible to you;’ let this glorious promise encourage you to pray much. Is the prize not worth the price? Shall we not give up all to follow Jesus in the path He opens to us here; shall we not, if need be, fast? Shall we not do anything that neither the body nor the world around hinder us in our great life-work,—having intercourse with our God in prayer, that we may become men of faith, whom He can use in His work of saving the world.