"You shall afflict your souls"—Leviticus 16:29.
We are commanded to fast on the tenth of Tishrei, Yom Kippur. We afflict ourselves by abstaining from food and drink, the nourishment of the soul.
We are also commanded to refrain on Yom Kippur from bathing, applying creams or ointments, wearing [leather] shoes and engaging in marital relations.