'Angel of the Lord' in the Bible

But the angel of the Lord by night opened the prison-doors, and brought them forth, and said,

And when forty years had expired, there appeared to him in the wilderness of mount Sina, an angel of the Lord in a flame of fire in a bush.

And the angel of the Lord spoke to Philip, saying, Arise, and go towards the south, to the way that goeth down from Jerusalem to Gaza, which is desert.

And behold, the angel of the Lord came upon him, and a light shined in the prison; and he smote Peter on the side, and raised him up, saying, Arise quickly. And his chains fell off from his hands.

And immediately the angel of the Lord smote him, because he gave not God the glory: and he was eaten by worms, and died.