Exodus 28:43

28:43 These must be on Aaron and his sons when they enter to the tent of meeting, or when they approach the altar to minister in the Holy Place, so that they bear no iniquity and die. It is to be a perpetual ordinance for him and for his descendants after him.

Exodus 33:19

33:19 And the Lord said, “I will make all my goodness pass before your face, and I will proclaim the Lord by name before you; I will be gracious to whom I will be gracious, I will show mercy to whom I will show mercy.”