'Angel of the Lord' in the Bible

But the angel of the LORD said to Elijah the Tishbite, "Arise, go up to meet the messengers of the king of Samaria, and tell them, 'Is it because there is no God in Israel, that you go to inquire of Baal Zebub, the god of Ekron?

The angel of the LORD said to Elijah, "Go down with him. Do not be afraid of him." He arose, and went down with him to the king.

It happened that night, that the angel of the LORD went out, and struck one hundred eighty-five thousand in the camp of the Assyrians. When men arose early in the morning, behold, these were all dead bodies.