Although the distinction is kept clear, the “angel of the Lord” is very closely identified with the Lord (who saw) and God (who called out) in this text (see Exodus 3:4). Moses could learn for himself about the depth of God’s glory and the plurality of persons in the Triune God, who, as one true God, is intimately involved in the lives of all his creatures.
2 And the angel of the LORD appeared to him in a flame of fire out of the midst of a bush. He looked, and behold, the bush was burning, yet it was not consumed.