Isaiah 58:4-5

4Yes! While you are fasting, you are also quarrelling and you are fighting. You hit each other with your fists. If you want your prayers to reach me in heaven, you cannot continue to fast in the way that you do today.

5The way that you fast does not please me at all: You make yourselves humble for a day. You bend down your head, like a piece of weak grass. You lie down on sackcloth and ashes. Do you think that you are really fasting when you do that? Do you think that it pleases me, the Lord?