'Angel of the Lord' in the Bible

And the angel of the Lord, having opened the doors of the prison during the night, and leading them out said,

And the angel of the Lord spoke to Philip, saying, Arise, and go towards the south unto the way going down from Jerusalem to Gaza; the same is desert.

And, behold, the angel of the Lord stood over him, and a light shone in the house; and having touched the side of Peter, he raised him up, saying; Rise up quickly. And his chains fell off from his hands.

And immediately the angel of the Lord smote him, because he gave not the glory to God; and being eaten by worms, he breathed out his soul.