Leviticus 10:6

Then Moses said to Aaron and his sons Eleazar and Ithamar, “Do not show grief by leaving your hair uncombed or by tearing your clothes. If you do, you will die, and the LORD’s anger will strike the whole community of Israel. However, the rest of the Israelites, your relatives, may mourn because of the LORD’s fiery destruction of Nadab and Abihu.