Exodus 19:21-22

21Then the Lord spoke to Moses, “Go down, warn the people, so that they do not break through [the barriers around the mountain] to the Lord to see [Me], and many of them perish [as a result].

22Also have the priests who approach the Lord consecrate (sanctify, set apart) themselves [for My sacred purpose], or else the Lord will break forth [in judgment] against them [and destroy them].”