Abishai — For though Joab only committed the murder, yet Abishai was guilty of it, because it was done with his consent, and counsel, and approbation. In battle — Which he did for his own necessary defence; and therefore it was no justification of this treacherous murder.
Related Commentaries of 2 Samuel 3:30
2 Samuel 3:30
30 So Joab and Abishai his brother slew Abner, because he had slain their brother Asahel at Gibeon in the battle.