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 Ils apportèrent la tête d'Isch-Boscheth à David dans Hébron, et ils dirent au roi: Voici la tête d'Isch-Boscheth, fils de Saül, ton ennemi, qui en voulait à ta vie; l'Eternel venge aujourd'hui le roi mon seigneur de Saül et de sa race.