'Angel of the Lord' in the Bible

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

And when forty years were completed, there appeared to him in the desert of mount Sinai the angel of the Lord, in a flame of fire in a bush.

Now the angel of the Lord spake to Philip, saying, Arise, and go towards the south, on the road which leads down from Jerusalem to Gaza: it is a wilderness.

And, lo! an angel of the Lord stood there, and light glared through the apartment: then with a stroke on Peter's side, he roused him up, and said, Arise quickly. And his chains fell from his hands.

But instantly the angel of the Lord smote him, because he gave not the glory to God: and being devoured with worms, he expired.