וְאַחֲרֵי־כֵ֞ן בָּ֣אוּ הַלְוִיִּ֗ם לַעֲבֹ֤ד אֶת־עֲבֹֽדָתָם֙ בְּאֹ֣הֶל מוֹעֵ֔ד לִפְנֵ֥י אַהֲרֹ֖ן וְלִפְנֵ֣י בָנָ֑יו כַּאֲשֶׁר֩ צִוָּ֨ה יְהוָ֤ה אֶת־מֹשֶׁה֙ עַל־הַלְוִיִּ֔ם כֵּ֖ן עָשׂ֥וּ לָהֶֽם׃ (ס)
此後，利未人進去，在亞倫和他兒子們面前，在會幕裡辦理他們的事奉；永恆者為利未人的事怎樣吩咐摩西，他們就照樣向利未人行了。
Rashi
כאשר צוה ה' ... כן עשו AS THE LORD HAD COMMANDED [MOSES CONCERNING THE LEVITES] SO DID THEY [UNTO THEM] — This is repeated (cf. v. 20) to tell the praise of those who performed the rite (Moses, Aaron and the Israelites) and those who had it performed on them (the Levites) — that none of them put any obstacle in the way.
Sforno
כאשר צוה ה' את משה על הלוים, G’d had commanded that the task of the Levites would be to stand guard, to form the choir chanting the psalms and to carry the parts of the Tabernacle whenever the situation called for this. They would be assigned their immediate duties by Aaron and his sons.
Chizkuni
כן עשו להם, “so they did unto them.” The Levites did so to the priests. An alternate interpretation: “so did Aaron and his sons to the Levites.” This interpretation is based on Numbers 4,19: וזאת עשו להם וחיו, “this is what you are to do unto them so that they will live.”