Isaiah 57-59
“Behold, on the day of your fast you find your desire, and drive hard all your workers” (58;3). God was angry with Israel because they had forgotten what He really cared about. They wanted His help and favor, so they fasted (58;2), but meanwhile they continued to oppress the poor. God rejected their religious rituals and called them to “undo the bands of the yoke, and to let the oppressed go free … to divide your bread with the hungry” (58:6-8). He called them to practical love.
The best evidence of our love for God is not fasting and sacrifice, but loving others (I John 4).