I Chronicles 15:4 Midrash

וַיֶּאֱסֹ֥ף דָּוִ֛יד אֶת־בְּנֵ֥י אַֽהֲרֹ֖ן וְאֶת־הַלְוִיִּֽם׃

And David gathered together the sons of Aaron, and the Levites;