Why did Rechab and Baanah claim that their actions have fulfilled the LORD’s vengeance against Saul?
Rechab and Baanah provided a theological motive for their actions. They claimed to be serving the Lord as instruments of divine wrath.1 It is not clear if they actually believed that their actions were consistent with the will of God, or if they simply mentioned the Lord so as to give the pretence of godly decision making. In either case they argued that their wicked deed was a divinely sanctioned act.2
8 and brought the head of Ish-bosheth to David at Hebron. And they said to the king, “Here is the head of Ish-bosheth, the son of Saul, your enemy, who sought your life. The LORD has avenged my lord the king this day on Saul and on his offspring.”