Moses
Numbers 8:6ESV·traditional attribution

“Take the Levites from among the people of Israel and cleanse them.

John Calvin Reformed @genevareformer

6. Take the Levites from among. To take them from among the children of Israel, is equivalent to subtracting them from the number of the people, that they might not be included in the general census, and accounted to be one of the tribes. This separation, then, as he will more clearly express a little further on, devoted the Levites to God for the service of the sanctuary.

Matthew Henry Presbyterian @wholebiblehenry

We read before of the separating of the Levites from among the children of Israel when they were numbered, and the numbering of them by themselves (Num 3:6, Num 3:15), that they might be employed in the service of the tabernacle. Now here we have directions given for their solemn ordination (Num 8:6), and the performance of it, Num 8:20.

Commenting on Numbers 8:5-26

John Gill Reformed Baptist @doctorgill

Take the Levites from among the children of Israel,.... Among whom they were mixed, as were all the tribes mixed together as Aben Ezra says, before they took their journey from Mount Sinai; however, from hence forward, they were distinguished from Israelites, as they are both in Scripture and in Jewish writings; see Ch1 9:2; though this seems to design no other but their appointment...