When Moses entered the Tent of Meeting to speak with Adonai, he heard the voice speaking to him from above the atonement cover atop the Ark of Testimony between the cheruvim. So he spoke with Him.
At that time Adonai set the tribe of Levi apart to carry the Ark of the Covenant of Adonai, to stand before Adonai to serve Him and to pronounce blessings in His Name—as is the case to this day.