Numbers 8:16

“For they [are] wholly given unto me from among the children of Israel, etc.] All of them, entirely, and most certainly; or, “given, given” f88, which is repeated for the confirmation of it; or because of their being twice given, first to the Lord by the children of Israel, and then by the Lord to Aaron and his sons, as Chaskuni; though Jarchi interprets it of the different parts of their service they were devoted to, given for bearing and carrying the vessels of the sanctuary, and given for the song, or to be singers in the temple: instead of such as open, every womb, [even instead of] the firstborn of all the children of Israel have I taken them unto me; (see Gill on “<040312>Numbers…”

“The Levites could only undertake their duties Numbers 3:0; Numbers 4:0 after the formal exchange of the Levites for the first-born Numbers 3:44-51. The distinction between the “consecration” of the priests Leviticus 8:0 and the less solemn “purification” Numbers 8:21 of the Levites is marked. These rites of purification are similar to those incumbent on the priests of Egypt. Numbers 8:7 Water of purifying - literally, “sin water:” i. e. water to cleanse from sin; no doubt taken from the laver of the sanctuary, which was used by the priests for purification before they went into the tabernacle to minister (compare Numbers 5:17; Exodus 30:18 ff). The “sprinkling” of so large a body of men…”

“wholly given: Nethunim, nethunim, "given, given." The word being repeated, "because," says Bp. Patrick, "the children of Israel had devoted them to him, by laying their hands upon them ( Num 8:10), and Aaron had waved them as a wave-offering to the Lord" ( Num 8:11). instead of such: Houbigant, on the authority of the Samaritan, reads, "instead of every first-born of the children of Israel, who openeth the womb." Num 3:12, Num 3:45 Numbers 8:17”