This passage uses strong language to show the problem with the people’s fasting. Their fasting was only outward religious behavior. They did not truly repent or do what is right.
Fasting without sincere hearts and righteous actions is empty. It is only for show.
People wore sackcloth and put ashes on their heads to show sorrow and mourning.
acceptable to the LORD?: The people wrongly believed that God would bless them if they performed the correct rituals. They thought the actions themselves would bring blessing.