Yahweh commands Moses to arrange the clans of the Levites around the tent of meeting and assigns them responsibilities.
Numbers 1: The Census
Yahweh commands Moses and Aaron to divide the Israelites according to tribe and count the fighting aged men. The total is 603,550. The Levites are counted separately as keepers of the tabernacle.
Exodus 6: God Promises Deliverance
Yahweh explains to Moses who he is and the covenant he made with Abraham, Isaac and Jacob. He tells Moses and Aaron to demand release of the Israelites.