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.
Aaron is to offer his own bull of sin offering, to make expiation for himself and for his household. Aaron shall take the two he-goats and let them stand before the Lord at the entrance of the Tent of Meeting; and he shall place lots upon the two goats, one marked for the Lord and the other marked for Azazel. Aaron shall bring forward the goat designated by lot for the Lord, which he is to offer as a sin offering; while the goat designated by lot for Azazel shall be left standing alive before the Lord, to make expiation with it and to send it off to the wilderness for Azazel.