“Behold, in the day of your fast you seek your own pleasure and oppress all your workers …” (v3). God told the Israelites that their fasting and prayers were useless, because they were mistreating their workers and the poor. God didn’t want their self-involved worship, He wanted real obedience. "Is not this the fast that I choose: 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 …?” (v6-8).
“Then shall your light break forth like the dawn…” (v8). If we belong to Christ, His own love for the world will shine brightly through our words and actions.