https://www.btstories.com/davids-mighty-men/

David had developed a group of 30 men that were the core of his fighting force. Joab’s brother, Abishai, led the group because of his bravery.

All 30 of these fighting men were proven warriors with skill and courage. But the mightiest of them were an inspiration to the entire army—they were called “the Three.” One of the Three personally killed 800 soldiers in a battle. Another stood firm when the rest of the army retreated. While they fell back, he turned and attacked the Philistines by himself. He fought so hard and so long that his hand stuck to his sword. The others finally came back, but only to plunder the dead bodies around him.