'Angel of the Lord' in the Bible

But during the night an angel of the Lord opened the prison doors and brought them out, and said,

And an angel of the Lord said to Philip, "Rise and proceed south to the road that runs down from Jerusalem to Gaza, crossing the Desert."

Suddenly an angel of the Lord stood by him, and a light shone in the cell; and, striking Peter on the side, he woke him and said, "Rise quickly." Instantly the chains dropped off his wrists.

Instantly an angel of the Lord struck him, because he had not given the glory to God, and being eaten up by worms, he died.