'Angel of the Lord' in the Bible

But when he was giving thought to these things, an angel of the Lord came to him in a dream, saying, Joseph, son of David, have no fear of taking Mary as your wife; because that which is in her body is of the Holy Spirit.

And Joseph did as the angel of the Lord had said to him, and took her as his wife;

And when they had gone, an angel of the Lord came to Joseph in a dream, saying, Get up and take the young child and his mother, and go into Egypt, and do not go from there till I give you word; for Herod will be searching for the young child to put him to death.

But when Herod was dead, an angel of the Lord came in a dream to Joseph in Egypt,

And there was a great earth-shock; for an angel of the Lord came down from heaven and, rolling back the stone, took his seat on it.