Why did the Son of God have to suffer for us? There was a great need, and it can be considered in a twofold way: in the first place, as a remedy for sin, and secondly, as an example of how to act.
It is a remedy, for in the face of all the evils which we incur on account of our sins, we have found relief through the passion of Christ. Yet, it is no less an example, for the passion of Christ completely suffices to fashion our lives. Whoever wishes to live perfectly should do nothing but disdain what Christ disdained on the cross and desire what he desired, for the cross exemplifies every virtue.