Abishai was the oldest son of Zeruiah, David's sister. He was the brother of Joab and Asahel). Abishai was the only one who accompanied David when he went to the camp of Saul and took the spear and the cruse of water from Saul's bolster.
He had the command of one of the three divisions of David's army at the battle with Absalom. He slew the Philistine giant Ishbi-benob, who threatened David's life. He was the chief of the second rank of the three "mighties" and on one occasion withstood 300 men, and slew them with his own spear.
Abishai means "father of (i.e., "desirous of") a gift".