'Angel of the Lord' in the Bible

But during the night an angel of the Lord opened the doors of the prison and led them [out] [and] said,

Now an angel of the Lord spoke to Philip, saying, "Get up and go toward the south on the road that goes down from Jerusalem to Gaza." (This is a desert [road].)

And behold, an angel of the Lord stood near [him], and a light shone in the prison cell. And striking Peter's side, he woke him up, saying, "Get up {quickly}!" And his chains fell off of [his] hands.

And immediately an angel of the Lord struck him down {because} he did not give the glory to God. And he was eaten by worms [and] died.