2 Samuel 3:30

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

2 Samuel 2:19-23

Asahel pursued after Abner; and in going he didn't turn to the right hand nor to the left from following Abner.

Proverbs 28:17

A man who is tormented by life blood will be a fugitive until death; no one will support him.

Acts 28:4

When the natives saw the creature hanging from his hand, they said one to another, "No doubt this man is a murderer, whom, though he has escaped from the sea, yet Justice has not allowed to live."

Treasury of Scripture Knowledge

Summary

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

Because

Bible References

Slew abner

Proverbs 28:17
A man who is tormented by life blood will be a fugitive until death; no one will support him.
Acts 28:4
When the natives saw the creature hanging from his hand, they said one to another, "No doubt this man is a murderer, whom, though he has escaped from the sea, yet Justice has not allowed to live."

Because

2 Samuel 2:19
Asahel pursued after Abner; and in going he didn't turn to the right hand nor to the left from following Abner.