Joab and Abishai; for though Joab only committed the murder, yet Abishai was guilty of it, because it was done with his consent, and counsel, and help, and approbation; for by these and such-like actions men are involved in the guilt of other men's sins, at least in God's judgment. Abner slew Asahel in the fury of battle, and for his own necessary defence; and therefore it was no justification of this unnecessary and treacherous murder in a time of peace.
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.