I have never done a Bible study on the topic of fasting, and I have never heard a sermon preached on the topic of fasting. Speaking to my brother the other day, he made this observation as well, asking me "What is fasting all about? Is that something we're supposed to do as Christians?" The Bible speaks of fasting, yet I find that Christians never seem to talk about it. My understanding of fasting has come directly from my regular reading of the Bible over the years, essentially without any external influence at all. So I thought I'd share with you the conclusions I've come to on the topic of fasting.
What I find as I read the Bible is that fasting is often linked with prayer, which might give the impression that sort of "adding" fasting to your prayer life will make your prayers more effective. But is this a voluntary denial of food in order to make the prayer more effective? I don't see how the denial of food would make prayer more effective. When the Bible teaches explicitly on how one is to pray effectively, it teaches that we should pray according to God's will (which is almost the same as saying "according to Scripture"), and that we must be living righteously. I'm not so sure that denying one's self food will affect our prayers. But what I have found in my own life is that, when I'm really stirred up to pray about something, I actually lose my appetite for food somewhat involuntarily; and I suspect that this is what fasting meant to those characters in the Bible which fasted. When we're distressed, or in grief, we often lose our appetites. I have a friend who, when his girlfriend broke up with him, ate nothing for days. He was simply too upset. What kinds of things might cause a Christian to become that upset that they lose their appetite? And wouldn't they be the kinds of things that a Christian might begin to pray about fervently? As I read the Bible, I find that fasting is almost always in response to some distress, as is the prayer associated with it. Some Biblical examples would be when David's first child to Bathsheba becomes sick; David prayed and fasted over that. And Saul, when he was confronted by God on the road to Damascus, ate no food for several days after. We can be distressed or grieved by our circumstances, but we can also be distressed over our spiritual state of being. When I as an unbeliever, for example, truly came to understand the weight of my sins, this for me was a time when I literally lost my appetite and couldn't eat. And we see fasting of this kind in the Bible as well. Another example would be when the King of Nineveh proclaimed a fast in response to the preaching of Jonah, which convicted the whole city of their sins.
Quite often in Scripture we find people, usually those in power, proclaiming a fast. This is often in the form of a king's edict that everyone in the city should fast, like in the case of Nineveh. Another example would be where Esther proclaimed a fast before she approached the King about the fate of her people. In such cases it seems as though a fast would not be involuntary, but would be deliberate, and obviously toward some purpose. But whereas I might fast in response to a distress which affects me, these proclamations are in response to some distress which affects the whole city or people. I have no doubt that culturally it was a symbol of expressing one's distress to God. But as always, it was not the outward gesture which was important to God, but the true attitude of the heart; and I think that if my city was preached to by Jonah, I might have gone into that "involuntary fast" over it whether the King proclaimed a national fast or not. It's a bit like when, in our culture, we commemorate certain tragic events with a minute of silence. One can keep silent for a minute and be thinking about all manner of things besides the dead soldiers, or what have you... but if the memory of those soldiers really does mean something to you, you might consider them during that minute as you ought.
Isaiah 58 is probably the most explicit text on fasting in the Bible. It begins with the people asking God "Why have we fasted, and you see it not? Why have we humbled ourselves, and you take no knowledge of it?" They possibly saw fasting as a way of making their prayers more effective. But God answers "Behold, in the day of your fast you seek your own pleasure, and oppress all your workers." And then, with words of correction, God says...
"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? Is it not to share your bread with the hungry and bring the homeless poor into your house; when you see the naked, to cover him, and not to hide yourself from your own flesh?" (Isaiah 58:6-7)
These things don't really have anything to do with denying one's self food, and that's God's point. God is not interested in asceticism, or self-denial, in some attempt to get closer to God. Rather, God is interested in good works. Going without food so that some starving person might have a meal; that might be the kind of fast which God is interested in. And to be so grieved over the spiritual state of those in the world around us that we lose our appetites, that's what Biblical fasting really is.
Then the disciples of John came to him, saying, "Why do we and the Pharisees fast, but your disciples do not fast?” And Jesus said to them, “Can the wedding guests mourn as long as the bridegroom is with them? The days will come when the bridegroom is taken away from them, and then they will fast." (Matthew 9:14-15)