The request of this verse is rather remarkable. Do not kill them, and we can add the words: not immediately. The purpose is that God’s people will not forget what God has done. Let the enemies first wander around a bit. The people should take the time to realize that God is acting justly. And so, the Lord becomes the shield of the author again, a safe fortress.
Compare our text with Jeremiah 11:18–20 “O Lord of hosts, who judges righteously.” David also did not take matters into his own hands. More than once he had the chance to kill Saul, his enemy, but he did not do it (1 Samuel 24:11–15). He left it in the hands to enforce justice.
12 Ne les tue pas, de peur que mon peuple ne l'oublie;Fais-les errer par ta puissance, et précipite-les,Seigneur, notre bouclier!