Burn only the proper incense on the altar and never use it for grain sacrifices or animal sacrifices or drink offerings.
Once a year Aaron must purify the altar by smearing on its four corners the blood of an animal sacrificed for sin, and this practice must always be followed. The altar is sacred because it is dedicated to me.
Nadab and Abihu were two of Aaron's sons, but they disobeyed the LORD by burning incense to him on a fire pan, when they were not supposed to.