When Moses went into the Meeting Tent to speak with the Lord, he heard the Lord speaking to him. The voice was coming from between the two gold creatures with wings that were above the lid of the Ark of the Agreement. In this way the Lord spoke with him.
At that time the Lord chose the tribe of Levi to carry the Ark of the Agreement with the Lord. They were to serve the Lord and to bless the people in his name, which they still do today.