The fact that it was the Lord who spoke to Moses indicates that God is the One, who took the initiative. He revealed himself to Moses—the man of his own choice—in an act of his own free will, and entirely on his own terms. This demonstrates the sovereignty, mercy, wisdom, and holiness of God.
1 The LORD spoke to Moses in the wilderness of Sinai, in the tent of meeting, on the first day of the second month, in the second year after they had come out of the land of Egypt, saying,