'Angel of the Lord' in the Bible

But just as this thought occurred to him, an angel of the Lord appeared to him in a dream, and said, "Joseph, descendant of David, do not fear to take Mary as your wife, for it is through the influence of the Holy Spirit that she has become an expectant mother.

So when Joseph awoke from his sleep, he did as the angel of the Lord directed him, and took her as his wife;

After they had gone, an angel of the Lord appeared to Joseph in a dream and said, "Wake up! Tenderly take the child and His mother, and escape to Egypt; stay there until I further direct you, for Herod is going to search for the child to destroy Him."

But after Herod died, an angel of the Lord in a dream appeared to Joseph in Egypt,

Now there had been a great earthquake. For an angel of the Lord came down from heaven and went and rolled the boulder back and remained sitting upon it.