Leviticus 16:1 provides the reader with the historical context for the Day of Atonement. It follows the deaths of Nadab and Abihu in Leviticus 10:1–20. These laws were given to Moses to prevent the untimely death of other priests as they served in the temple.
1 The LORD spoke to Moses after the death of the two sons of Aaron, when they drew near before the LORD and died,