Isaiah 58:5

Is it such a fast that I have chosen? a day for a man to afflict his soul? Could the Lord accept their fasting as an expression of repentance? Is it to bow down his head as a bulrush, affecting a sorrow which he was far from feeling, and to spread sackcloth and ashes under him? to make that his bed. Wilt thou call this a fast and an acceptable day to the Lord? All external evidences of sorrow and mourning mean nothing if the heart and mind are not affected, if they do not flow out of a repentant heart. The fasting which pleases the Lord is of an entirely different kind.