2 Samuel 3:30

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

2 Samuel 2:19-23

And Asahel pursued Abner, and as he went, he turned neither to the right hand nor to the left from following Abner.

Proverbs 28:17

If one is burdened with the blood of another, he will be a fugitive until death; let no one help him.

Acts 28:4

When the native people saw the creature hanging from his hand, they said to one another, "No doubt this man is a murderer. Though he has escaped from the sea, Justice has not allowed him 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
If one is burdened with the blood of another, he will be a fugitive until death; let no one help him.
Acts 28:4
When the native people saw the creature hanging from his hand, they said to one another, "No doubt this man is a murderer. Though he has escaped from the sea, Justice has not allowed him to live."

Because

2 Samuel 2:19
And Asahel pursued Abner, and as he went, he turned neither to the right hand nor to the left from following Abner.

The Holy Bible, English Standard Version® copyright © 2001 by Crossway Bibles, a publishing ministry of Good News Publishers.