'Angel of the Lord' in the Bible

But an angel of the Lord opened the jail doors in the night and let them out, and said to them,

But an angel of the Lord said to Philip, "Get up and go south, by the road that runs from Jerusalem to Gaza." (The town is now deserted.)

when an angel of the Lord stood at his side, and a light shone in the room, and striking Peter on the side, he woke him, and said to him, "Get up quickly!" The chains dropped from his hands,

But the angel of the Lord struck him down immediately, because he did not give the honor to God; and he was eaten by worms and died.