Joel 12:12-13 says, “Therefore also now, saith the Lord, turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning: And rend your heart, and not your garments, and turn unto the Lord your God: for he is gracious and merciful, slow to anger, and of great kindness, and repenteth him of the evil.”
Richard J. Foster said, “Regular or weekly fasting has had such a profound effect in the lives of some that they have sought to find a biblical command for it so that it may be urged upon all Christians. The search is in vain. There simply are no biblical laws that command regular fasting. Our freedom in the gospel, however, does not mean license; it means opportunity. Since there are no laws to bind us, we are free to fast on any day. Freedom for the apostle Paul meant that he was engaged in ‘fastings often.’ We should always bear in mind the apostolic counsel in Galatians 5:13, ‘Do not use your freedom as an opportunity for the flesh.’”
You can listen to over 150 podcasts that I did on fasting at Prayer Motivator Devotional.com. When you get there, click on the “Fasting Edition” link.