What do we learn from "Lo la'Netzach Yariv"?
Radak: If He quarreled with us and put us in Galus, it will not be forever. He will have mercy on us and raise us from Galus.
Malbim: There is a difference between la'Netzach and l'Olam. L'Olam refers to permanence of the body; la'Netzach refers to permanence of the Nefesh. There is a difference between Yariv and Yitur. Yariv is to quarrel with and punish him. Noter is guarding the hatred in the heart, and not punishing immediately. Amidst Hashem's Chesed, when He is Meriv with a man and punishes him, He will not be Meriv with him in the world to come, to cut off the permanence of is Nefesh. He is Meriv only in this world, and punishes him here, in the temporary, non-eternal world, lest He punish the Nefesh. Its punishment pertains to eternity.
Why does it say "Lo l'Olam Yitur"?
Malbim: It is better that He is Meriv and punishes in this world, lest he need to punish in the world to come.
