Commentaire sur Les Nombres 8:9

והקהלת את כל עדת AND THOU SHALT GATHER THE WHOLE ASSEMBLY [OF THE CHILDREN OF ISRAEL] TOGETHER — Because the Levites were made, so to speak, an expiatory offering in their stead, let them come and stand at their offering and put their hands upon them (the Levites) as is prescribed in the case of an offering (cf. Leviticus 1:4).

And stand near. Even though the Levites were only an atonement-offering for the firstborn, as explained above, nonetheless, since the firstborn were part of the congregation of Yisroel, they were termed the entire congregation of Yisroel as if they were all of Yisroel.

.והקרבת את הלוים לפני אהל מועד , “you shall present the Levites at the entrance of the Tent of Meeting;” we find a similar construction in Leviticus 14,11, where the priest is presenting the person to be purified at the entrance of the Tabernacle, i.e. “before the Lord.”