# You must purify them. You must offer them as a wave offering

"But first, you must purify them. You must offer them as a wave offering". Yahweh repeats these things to emphasize their importance. This must happen before the Levites go to serve at the tent of meeting.  

# You must offer them as a wave offering

"You must dedicate them to me, as if you were presenting a wave offering to me". Aaron was to present the Levites to Yahweh as if they were a wave offering to him.