הַקְרֵב֙ אֶת־מַטֵּ֣ה לֵוִ֔י וְֽהַעֲמַדְתָּ֣ אֹת֔וֹ לִפְנֵ֖י אַהֲרֹ֣ן הַכֹּהֵ֑ן וְשֵׁרְת֖וּ אֹתֽוֹ׃
’Bring the tribe of Levi near, and set them before Aaron the priest, that they may minister unto him.
Read kabbalistic (mystical) interpretation of Numbers 3:6: and classical mystical sources.