St. Leo the Great was Pope from 440-461. His preaching was eloquent and magesterial - not unlike that of his current successor in the See of Rome. This excerpt from one of his most famous Christmas sermons (Sermo 1 in Nativitate Domini, 1-3; PL 54, 190-193) is used in the Office of Readings for Christmas Day, and is one which I always find very impressive and enlivening.
Dearly beloved, today our Saviour is born; let us rejoice. Sadness should have no place on the birthday of life. The fear of death has been swallowed up; life brings us joy with the promise of eternal happiness.
No one is shut out from this joy; all share the same reason for rejoicing. Our Lord, victor over sin and death, finding no man free from sin, came to free us all. Let the saint rejoice as he sees the palm of victory at hand. Let the sinner be glad as he receives the offer of forgiveness. Let the pagan take courage as he is summoned to life.
In the fullness of time, chosen in the unfathomable depths of God’s wisdom, the Son of God took for himself our common humanity in order to reconcile it with its creator. He came to overthrow the devil, the origin of death, in that very nature by which he had overthrown mankind.
And so at the birth of our Lord the angels sing in joy: Glory to God in the highest, and they proclaim Peace to men of good will as they see the heavenly Jerusalem being built from all the nations of the world. When the angels on high are so exultant at this marvellous work of God’s goodness, what joy should it not bring to the lowly hearts of men?
Beloved, let us give thanks to God the Father, through his Son, in the Holy Spirit, because in his great love for us he took pity on us, and when we were dead in our sins he brought us to life with Christ, so that in him we might be a new creation. Let us throw off our old nature and all its ways and, as we have come to birth in Christ, let us renounce the works of the flesh.
Christian, remember your dignity, and now that you share in God’s own nature, do not return by sin to your former base condition. Bear in mind who is your head and of whose body you are a member. Do not forget that you have been rescued from the power of darkness and brought into the light of God’s kingdom.
Through the sacrament of baptism you have become a temple of the Holy Spirit. Do not drive away so great a guest by evil conduct and become again a slave to the devil, for your liberty was bought by the blood of Christ.