Rashi on Isaiah
the chastisement of our welfare was upon him The chastisement due to the welfare that we enjoyed, came upon him, for he was chastised so that there be peace for the entire world.
Ibn Ezra on Isaiah
The chastisement of our peace was upon him. The chastisement was inflicted upon him for the purpose of prolonging our peace, as we see; for With his stripes we are healed.