'Angel of the Lord' in the Bible

But an angel of the Lord, by night, opened the prison doors; and, having led them out, said,

But an angel of the Lord spake to Philip, saying, "Arise, and go toward the south, on the way that leads down from Jerusalem to Gaza:" this is a wilderness.

And, behold, an angel of the Lord stood by him, and a light shined in the cell; and, smiting the side of Peter, he raised him up, saying, "Rise up quickly!" And his chains fell off from his hands.

And immediately an angel of the Lord smote him, because he did not give God the glory; and, having been eaten by worms, he expired.