I. When we were yet sinners, Christ came to save
Although I know, dearly-beloved, that you are fully aware of the purpose of today's festival, and that the words of the Gospel have according to use unfolded it to you, yet that nothing may be omitted on our part, I shall venture to say on the subject what the Lord has put in my mouth: so that in our common joy the devotion of our hearts may be so much the more sincere as the reason of our keeping the feast is better understood. The providential Mercy of God, having determined to succour the perishing world in these latter times, fore-ordained the salvation of all nations in the Person of Christ; in order that, because all nations had long been turned aside from the worship of the true God by wicked error, and even God's peculiar people Israel had nearly entirely fallen away from the enactments of the Law, now that all were shut up under sin, He might have mercy upon all.
For as justice was everywhere failing and the whole world was given over to vanity and wickedness, if the Divine Power had not deferred its judgment, the whole of mankind would have received the sentence of damnation. But wrath was changed to forgiveness, and, that the greatness of the Grace to be displayed might be the more conspicuous, it pleased God, to apply the mystery of remission to the abolishing of men's sins at a time when no one could boast of his own merits.
Source: Sermons (New Advent)