In Exodus 28–29, the Lord gave Moses detailed instructions for clothing and ordaining Aaron and his sons as priests. In Exodus 39:1–31; 40:12–16; and Leviticus 8, they followed these commands. Moses did not only tell them the instructions. He performed the ceremonies to show the priests exactly what to do, as the Lord had commanded him (8:9, 13, 17, 21, 29). Since disobedience could lead to death, God ensured the priests understood their duties clearly.