'Angel of the Lord' in the Bible

But an angel of the Lord opened the prison-doors, by night, and bringing them forth,

And forty years being expired, the angel of the Lord appeared to him, in the wilderness, in a flame of fire in a bush.

And an angel of the Lord spake to Philip, saying, Arise and go toward the south by the way leading down from Jerusalem to Gaza, which is desert.

He saw plainly in a vision, about the ninth hour of the day, an angel of the Lord coming in to him, and saying to him, Cornelius.

And behold, an angel of the Lord stood over him, and light shined in the house: and smiting Peter on the side he waked him, saying, Rise up quickly. And his chains fell off from his hands.

And immediately an angel of the Lord smote him, because he gave not God the glory; and being eaten by worms, he expired.