ab'-i-shi, a-bi'-shi ('abhishai, in Ch 'abhshai; meaning is doubtful, probably "my father is Jesse," BDB):
Son of Zeruiah, David's sister, and one of the three famous brothers, of whom Joab and Asahel were the other two (2 Samuel 2:18). He was chief of the second group of three among David's "mighty men" (2 Samuel 23:18).
He first appears with David, who was in the Wilderness of Ziph, to escape Saul. When David called for a volunteer to go down into Saul's camp by night, Abishai responded, and counseled the killing of Saul when they came upon the sleeping king (1 Samuel 26:6-9). In the skirmish between the men of Ishbosheth and the men of David at Gibeon, in which Asahel was killed by Abner, Abishai was present (2 Samuel 2:18,24). He was with and aided Joab in the cruel and indefensible murder of Abner, in revenge for their brother Asahel (2 Samuel 3:30).
In David's campaign against the allied Ammonites and Syrians, Abishai led the attack upon the Ammonites, while Joab met the Syrians; the battle was a great victory for Israel (2 Samuel 10:10-14). He was always faithful to David, and remained with him, as he fled from Absalom. When Shimei, of the house of Saul, cursed the fleeing king, Abishai characteristically wished to kill him at once (2 Samuel 16:8,9); and when the king returned victorious Abishai advised the rejection of Shimei's penitence, and his immediate execution (2 Samuel 19:21).
In the battle with Absalom's army at Mahanaim Abishai led one division of David's army, Joab and Ittai commanding the other two (2 Samuel 18:2). With Joab he put down the revolt against David of Sheba, a man of Benjamin (2 Samuel 20:6,10), at which Joab treacherously slew Amasa his cousin and rival, as he had likewise murdered Abner, Abishai no doubt being party to the crime. In a battle with the Philistines late in his life, David was faint, being now an old man, and was in danger of death at the hands of the Philistine giant Ishbihenob when Abishai came to his rescue and killed the giant (2 Samuel 21:17). In the list of David's heroes (2 Samuel 23) Abishai's right to leadership of the "second three" is based upon his overthrowing three hundred men with his spear (2 Samuel 23:18). He does not appear in the struggle of Adonijah against Solomon, in which Joab was the leader, and therefore is supposed to have died before that time.
He was an impetuous, courageous man, but less cunning than his more famous brother Joab, although just as cruel and relentless toward rival or foe. David understood and feared their hardness and cruelty. Abishai's best trait was his unswerving loyalty to his kinsman, David.