'Angel of the Lord' in the Bible

'Choose thee either three years' famishment, or three months to be consumed of thine adversaries, the sword of thine enemies overtaking thee: or else the sword of the LORD three days and pestilence in the land, the angel of the LORD destroying throughout all the coasts of Israel.' And now advise thyself what word I shall bring again unto him that sent me."

And God sent the angel to Jerusalem to destroy it. And as he was about to destroy, the LORD beheld and had compassion on the wretchedness, and said to the angel that destroyed, "It is enough, now cease thine hand." And the angel of the LORD stood by the threshing floor of Ornan the Jebusite.

And David lifted up his eyes and saw the angel of the LORD stand between the earth and heaven with a drawn sword in his hand stretched out toward Jerusalem. Then fell David and the elders of Israel, clothed in sack, upon their faces.

And David could not go before it to seek God, because he was afraid of the sword of the Angel of the LORD.