פירוש על במדבר 8:20

ויעש משה ואהרן וכל עדת וגו׳ AND MOSES AND AARON AND ALL THE CONGREGATION … DID [TO THE LEVITES ACCORDING UNTO ALL THAT THE LORD COMMANDED MOSES] — i.e. Moses presented them (v. 13), Aaron made the waving with them (v. 11) and the Israelites put their hands (v. 10) upon the Levites’ heads (cf., however, Ibn Ezra).

ויעש משה ואהרן וכל עדת בני ישראל ללוים, the prefix ל in the word ללוים means “on behalf of, in aid of them.” They assisted with the shaving, the laundering of their clothing, as well as in preparation of the requisite offering.

ויעש משה…וכל עדת בני ישראל..כן עשו להם בני ישראל. And Moses and Aaron and the whole congregation of Israel did….so the children of Israel did to them (the Levites). Why did the Torah have to repeat the line: "so they did?" Why did the Torah speak about the "whole community of the children of Israel" at the beginning of the verse, whereas at its conclusion it only speaks of "the children of Israel?" It appears that the line כן עשו בני ישראל is repeated as it is a reference to the firstborn who are being complimented for agreeing to their new status seeing they were the ones who lost many privileges due to this change. This is also the reason that at the end of the verse the Torah did not speak of "the whole community of Israel," since only the firstborn of the Israelites were meant.