Fasting is an important spiritual tool that the Bible teaches us to do in both the Old Testament and the New Testament.
Isaiah 58:3-7 “Why have we fasted, and you see it not? Why have we humbled ourselves, and you take no knowledge of it?’ Behold, in the day of your fast you seek your own pleasure, and oppress all your workers. Behold, you fast only to quarrel and to fight and to hit with a wicked fist. Fasting like yours this day will not make your voice to be heard on high. Is such the fast that I choose, a day for a person to humble himself? Is it to bow down his head like a reed, and to spread sackcloth and ashes under him? Will you call this a fast, and a day acceptable to the Lord? “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?”
Trust in the Lord with all your heart,
And lean not on your own understanding;
In all your ways acknowledge Him,
And He shall direct your paths.