Charles Ellicott 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)

When the Lord saw ... God called. —Hebrew, When Jehovah saw, Elohim called. The German theory of two authors of Exodus, one Jehovistic and the other Elohistic, is completely refuted by this passage; for it is impossible to ascribe one clause of a sentence to one author, and the next to another. If originally the same term had been used in both places, a reviser would not have altered one without altering both.

Moses, Moses. —Compare Genesis 26:11; 1 Samuel 3:10; and Acts 9:4. The repetition marks extreme urgency.