In Leviticus 16, a bull is sacrificed as a sin offering for Aaron.
The ritual belongs to Yom Kippur, the Day of Atonement. Before entering the Holy of Holies, Aaron, Israel's first high priest, was instructed to bring a bull for his own sin offering and a ram for a burnt offering. The bull addressed Aaron and his household, while separate goats represented the wider Israelite community.
The bull was not the same animal as the famous scapegoat. Two male goats were selected for the people: one was sacrificed to the LORD, and the other was sent into the wilderness for Azazel, symbolically carrying away Israel's sins. This distinction is a common source of confusion.
The ritual described in Leviticus was associated with the Tabernacle and later the Jerusalem Temples. The Yom Kippur Temple service is no longer performed because the Second Temple was destroyed in 70 CE, but its order remains central to rabbinic discussions in tractate Yoma and to synagogue readings about Yom Kippur.