קַ֚ח אֶת־הַלְוִיִּ֔ם מִתּ֖וֹךְ בְּנֵ֣י יִשְׂרָאֵ֑ל וְטִהַרְתָּ֖ אֹתָֽם׃
你要從以色列人中取利未人,使他們潔淨。
Rashi
קח את הלוים means, win them over with fine words: “Happy are ye that ye are privileged to be servants of the Omnipresent!” (cf. Rashi on Leviticus 8:2.)
Or HaChaim
קח את הלוים, "Take the Levites! etc." Rashi explains that the word "take!" means by means of words. Apparently Rashi means that Moses was to separate the Levites from the camps of the Israelites and make a separate camp for them seeing the Levites had to guard their ritual purity more than ordinary Israelites. The proof is to be found in the words וטהרת אותם, "and purify them!" Clearly what concerns the Torah at this point is the need for the Levites to maintain a state of ritual purity.
Rabbeinu Bahya
קח את הלוים מתוך בני ישראל, “take the Levites from among the Children of Israel, etc.” The paragraph dealing with the separation of the Levites was written immediately after that of the Menorah, as the former was the exclusive domain of the priests, whereas now the Torah prepares the Levites for assuming their duties. The next paragraph deals with the Passover as an historical commandment remembering the Exodus, a commandment involving every single Israelite. This is the meaning of 9,2: “The Israelites shall make the Passover.” You will observe therefore that these paragraphs have been arranged in a careful manner in a descending order of those to whom they apply, i.e. the Priest, the Levite, the Israelite. The reason that G’d had to say: “take the Levites from among etc., etc.,” was that until then they had been an integral part of the other tribes.