2 Samuel 3:30

For Joab and Abessa his brother laid wait continually for Abenner, because he killed Asael their brother at Gabaon in the battle.

So Joab and Abishai his brother slew Abner, because he had slain their brother Asahel at Gibeon in the battle.

So Joab and Abishai his brother killed Abner, because he had killed their brother Asahel at Gibeon in the battle.