Abishai in Smiths Bible Dictionary

(father of a gift), The eldest of the three sons of Zeruiah, David's sister, and brother to Joab and Asahel. 1Ch 2:16 Like his two brothers he was the devoted follower of David. He was his companion in the desperate night expedition to the camp of Saul. 1Sa 26:6-9 (B.C. 1055.) On the outbreak of Absalom's rebellion he remained true to the king,a nd commanded a third part of the army in the decisive battle against Absalom. He rescued David from the hands of the gigantic Philistine, Ishbi-benob. 2Sa 21:17 His personal prowess on this, as on another occasion, when he fought singlehanded against three hundred, won for him a place as captain of the second three of David's mighty men. 2Sa 23:18; 1Ch 11:20

Link: https://bible-history.com/smiths/A/Abishai+or+Abisha-i/