God calls Moses by name. The fact that God calls his name twice is a sign God comes with an important and urgent message. This is also the way in which God called Abraham (Genesis 22:11), Samuel (1 Samuel 3:10), and Saul (Acts 9:4). Prophets were called by God to tell people the Word of God (Moses, Samuel, Isaiah, Jeremiah, and others). Here Moses is called to tell Israel the good news of liberation and to bring them out of Egypt.
Moses’ answer, Here I am,
is of a servant who gets an order and obeys (see Genesis 22:1; 1 Samuel 3:4, 1 Samuel 3:6–10).
4 When the LORD saw that he turned aside to see, God called to him out of the bush, “Moses, Moses!” And he said, “Here I am.”