Berean Standard Bible (BSB)
(Joab and his brother Abishai murdered Abner because he had killed their brother Asahel in the battle at Gibeon.)
World English Bible (WEB)
So Joab and Abishai his brother killed Abner, because he had killed their brother Asahel at Gibeon in the battle.
Strong's King James
So Joab{H3097} and Abishai{H52} his brother{H251} slew{H2026}{(H8804)} Abner{H74}, because he had slain{H4191}{(H8689)} their brother{H251} Asahel{H6214} at Gibeon{H1391} in the battle{H4421}.
The F.O.G *
The F.O.G Message *
Young's Literal Translation
And Joab and Abishai his brother slew Abner because that he put to death Asahel their brother, in Gibeon, in battle.