This reading is from the Torah portion read on Yom Kippur. The complete reading for Yom Kippur is Leviticus 16:1-34 and Numbers 29:7-11.
The Lord spoke to Moses after the death of the two sons of Aaron who died when they drew too close to the presence of the Lord. The Lord said to Moses:
Tell your brother Aaron that he is not to come at will into the Shrine behind the curtain, in front of the cover that is upon the ark, lest he die; for I appear in the cloud over the cover. Thus only shall Aaron enter the Shrine: with a bull of the herd for a sin offering and a ram for a burnt offering. He shall be dressed in a sacral linen tunic, with linen breeches next to his flesh, and be girt with a linen sash, and he shall wear a linen turban. They are sacral vestments; he shall bathe his body in water and then put them on. And from the Israelite community he shall take two he-goats for a sin offering and a ram for a burnt offering.