'Angel of the Lord' in the Bible

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

Then an angel of the Lord said to Philip, "Get up and go south on the road that goes down from Jerusalem to Gaza." (This is a desert road.)

Suddenly an angel of the Lord appeared, and a light shone in the prison cell. He struck Peter on the side and woke him up, saying, "Get up quickly!" And the chains fell off Peter's wrists.

Immediately an angel of the Lord struck Herod down because he did not give the glory to God, and he was eaten by worms and died.