Fasting usually results in God’s gracious response. But not always. Isaiah 58 relates the Lord’s frustration with Jewish religious leadership. “‘Why have we fasted,’ they say, ‘and you have not seen it? Why have we humbled ourselves, and you have not noticed?’ “Yet on 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 this the kind of fast I have chosen, only a day for a man to humble himself? Is it only for bowing one’s head like a reed and for lying on sackcloth and ashes? Is that what you call a fast, a day acceptable to the Lord? Is not this the kind of fasting I have chosen: to loose the chains of injustice and untie the cords of the yoke, to set the oppressed free and break every yoke? Is it not to share your food with the hungry and to provide the poor wanderer with shelter— when you see the naked, to clothe him, and not to turn away from your own flesh and blood?”
The reader of Scripture can perceive that the Jewish leadership had been going through the motions of repentance without actually being repentant. Isaiah’s point to them is clear. Fasting is useless if it is not a heartfelt attempt to humble oneself before God. Merely abstaining from food will never gain God’s approval. Even if it is accompanied by sackcloth and ashes. It is impossible to try to “empty oneself” apart from actual repentance. It just cannot be done in God’s sight. Fasting just for the sake of abstaining from food is its own reward – it gives the body time to cleanse and heal. So do not expect an additional spiritual reward if there is no spiritual effort accompanying it. Rather, the Lord tells us it is better that we be concerned with the physical well being of others than to lay around in sackcloth and ashes.
The whole point of fasting is to break bonds. Breaking the bond that food has on your own body is just an outward manifestation of the reality of breaking the spiritual bonds holding down others. It is an act of humility, because the one suffers for and on account of the other. Fasting is a weapon of spiritual warfare. It has the power to loose chains, untie cords, to set people free and to break yokes of slavery to ungodliness. But only if and when the practitioner has first emptied themselves in humility (ensuring their voice is clear and loud in God’s ears) and is seeking what God wants (ensuring His voice is clear and loud in their ears), not their own desire.
What God wants is clear from Scripture. He wants His Kingdom (including the freedom of His people) and His rule (including the destruction of that which is opposed to Him) and His glory (including the praise His people give Him for freeing them and destroying what held them in bondage). What God does not want is attention and glory for the impure. To this point Jesus instructs, “But when you fast, put oil on your head and wash your face, so that it will not be obvious to men that you are fasting, but only to your Father, who is unseen; and your Father, who sees what is done in secret, will reward you.” In saying that, recognize that the Lord is not prescribing hypocrisy. Quite the opposite. Repentance must be a matter of the heart that results in outward action, not outward action alone.
Great prophets such as Amos, Jeremiah, Isaiah, and Hosea came to the people to remind them that God demands genuine, godly sorrow that comes from the heart. The bottom line was this: the people were called to rend their hearts, not their garments. When the prophets exhorted the people in this way, they weren’t opposing the practice of the rending of garments, but were saying that it’s not enough to tear your clothes as a sign of repentance; the heart must be torn as well. When we realize that we have offended God, we must feel this rupture of our soul.R.C. Sproul
The next time you fast, keep it between you and the Lord.