Leviticus 16:13

Lev 16:13 And he shall put the incense upon the fire before the LORD, that the cloud of the incense may cover the mercy seat that [is] upon the testimony, that he die not:

Ver. 13. May cover the mercy seat. ] And so be as a screen betwixt the priest and those everlasting burnings: or as a cloud to darken the glory of their shining, for the high priest’s safety.