Albert Barnes Commentary Exodus 3:4

"And when Jehovah saw that he turned aside to see, God called unto him out of the midst of the bush, and said, Moses, Moses. And he said, Here am I." — Exodus 3:4 (ASV)

The Lord saw - The interchange of the two divine names is to be observed; “Jehovah” (Yahweh) saw, “God” called.