From Tractate 121 on John (419)
Mary Magdalene came and told the disciples, “I have seen the Lord, and he has spoken these things to me.” Then the same day at evening, being the first day of the week, when the doors were shut where the disciples were… Jesus came and stood in their midst. And he says to them, “Peace be to you.” And when he had so said, he showed them his hands and his side. For nails had pierced his hands, a spear had laid open his side: and there the marks of the wounds are preserved for healing the hearts of the doubting.
But the shutting of doors presented no obstacle to the matter of his body, wherein Godhead resided. He indeed could enter without their being opened, by whose birth the virginity of his mother remained inviolate, then were the disciples glad when they saw the Lord. Then Jesus said to them again, “Peace be to you.” Reiteration is confirmation; for he himself gives by the prophet a promised peace upon peace. “As the Father has sent me,” Jesus adds, “even so send I you.”
We know the Son to be equal to the Father; but here we recognize the words of the Mediator. For he exhibits himself as occupying a middle position when Jesus says, “he me,” and “I you.” And when Jesus had said this, he breathed on them, and said to them, “Receive the Holy Ghost.” By breathing on them Jesus signified that the Holy Spirit was the Spirit, not of the Father alone, but likewise his own. “Whose sins,” he continues, “you remit, they are remitted; and whose sins you retain, they are retained.” The Church’s love, which is shed abroad in our hearts by the Holy Spirit, discharges the sins of all who are partakers with itself, but retains the sins of those who have no participation therein. Therefore it is, that after saying, “Receive the Holy Ghost,” Jesus straightway added this regarding the remission and retention of sins.
St. Augustine (354-430) was a theologian and philosopher who served as Bishop of Hippo Regius in North Africa. He was a voluminous author, whose writings about God’s grace, the Sacraments, and the Church have been profoundly influential in the development of Western Christianity. The Tractates on John are based on exegetical sermons he delivered in his cathedral. His feast day is August 26.