The answer is: Joab

2 Sam 3:26-30 - Joab thought Abner was a spy

Abner's murder is a particularly compelling story in the tumultuous world of ancient Israel, showcasing the struggles for power and allegiances. Joab, being David’s nephew and head of his army, saw Abner—who had just made overtures towards David—as a threat, suspecting him of espionage. This pent-up suspicion stems from the tribal divisions that persisted long before David came to power, where loyalty was fragile and relationships were complex.

Joab approached Abner under the guise of peace, only to strike him down in a shocking act of betrayal. This episode raises the curtain on the darker side of political ambition. Joab's actions have sparked debate among readers: Is he truly a villain, or did he believe he was protecting David’s reign?

Interestingly, Abner means “father of light.” His efforts to unite the tribes reflect a search for clarity in Israel's tribalism. Just ironically, his fate became a part of the turbulent sidined scene—a rather dark twist for one aiming for peace.

For those intrigued by Joab's volatile character, remember that he played a critical role in other significant events during David’s reign. His personal interactions with David illuminate just how loyalty, betrayal, and ambition intertwined in the fabric of leadership. Ultimately, tales like this remind us of the moral complexities woven through narratives in the Bible, wherein personal and political dynamics can shift unexpectedly, often leading to dire outcomes.