Isaiah is the book of the Bible read as the haftarah on Yom Kippur morning.
The reading is Isaiah 57:14–58:14 in most Jewish liturgical traditions. It begins with words of consolation and then turns to a sharp critique of empty fasting: Isaiah says that abstaining from food means little if people exploit workers, quarrel, or neglect the vulnerable.
That message fits Yom Kippur's central themes of repentance, ethical repair, and reconciliation. The day is not presented merely as a ritual fast; its prophetic reading insists that religious observance must be joined to justice, generosity, and freeing people from oppression.
A common mix-up is Jonah, which is traditionally read during the afternoon service, not the morning service. Isaiah 58 is also associated with the famous biblical idea of choosing a fast that feeds the hungry and helps the oppressed, making it one of the holiday's most recognizable prophetic passages.