'Angel of the Lord' in the Bible

Three years when there will not be enough food; or three months of war, when you will go in flight before your haters, being in great danger of the sword; or three days of the sword of the Lord, disease in the land, and the angel of the Lord taking destruction through all the land of Israel. Now give thought to the answer I am to take back to him who sent me.

And God sent an angel to Jerusalem for its destruction: and when he was about to do so, the Lord saw, and had regret for the evil, and said to the angel of destruction, It is enough; do no more. Now the angel of the Lord was by the grain-floor of Ornan the Jebusite.

And David, lifting up his eyes, saw the angel of the Lord there between earth and heaven, with an uncovered sword in his hand stretched out over Jerusalem. Then David and the responsible men, clothed in haircloth, went down on their faces.

Then the angel of the Lord gave orders to Gad to say to David that he was to go and put up an altar to the Lord on the grain-floor of Ornan the Jebusite.

But David was not able to go before it to get directions from the Lord, so great was his fear of the sword of the angel of the Lord.