John Gill Commentary Numbers 8:20

"Thus did Moses, and Aaron, and all the congregation of the children of Israel, unto the Levites: according unto all that Jehovah commanded Moses touching the Levites, so did the children of Israel unto them." — Numbers 8:20 (ASV)

And Moses and Aaron, and all the congregation of the children
of Israel
The several parties concerned in the consecration of the Levites: these did to the Levites according unto all that the Lord commanded Moses ,
so did the children of Israel unto them :

which, as Jarchi notes, is said to the praise of them that did it, and of what was done by them; everything was done that was ordered, and in the manner in which it was prescribed;

Moses sprinkled, or ordered to be sprinkled, the water of purification on them, and set them before the tabernacle, and before the Lord; the children of Israel laid their hands on them, and Aaron waved them, offered the sacrifices for them.