Patristic Wisdom: Looking to the Second Sunday of Easter

Then, the same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled, for fear of the Jews, Jesus came and stood in the midst, and said to them, “Peace be with you.” When He had said this, He showed them His hands and His side. Then the disciples were glad when they saw the Lord. So Jesus said to them again, “Peace to you! As the Father has sent Me, I also send you.” And when He had said this, He breathed on them, and said to them, “Receive the Holy Spirit. If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained.” (John 20:19–31)

After dignifying the holy Apostles with the glorious distinction of the apostleship, and appointing them ministers and priests of the Divine Altar, as I have just said, He at once sanctifies them by entrusting His Spirit unto them, through the outward sign of His Breath, that we might be firmly convinced that the Holy Spirit is not alien to the Son, but Consubstantial with Him, and through Him proceeding from the Father; He shows that the gift of the Spirit necessarily attends those who are ordained by Him to be Apostles of God. And why? Because they could have done nothing pleasing unto God, and could not have triumphed over the snares of sin, if they had not been clothed with power from on high, and been transformed into something other than they were before.

Cyril of Alexandria, Commentary on the Gospel of John 12.1

After His resurrection He bestows equal power upon all the Apostles, and says: “As the Father has sent me, I also send you. Receive the Holy Spirit: if you forgive the sins of anyone, they will be forgiven him; if you retain the sins of anyone, they will be retained,” yet that He might display unity, He established by His authority the origin of the same unity as beginning from one. Surely the rest of the Apostles also were that which Peter was, endowed with an equal partnership of office and of power, but the beginning proceeds from unity, that the Church of Christ may be shown to be one. This one Church, also, the Holy Spirit in the Song of Songs designates in the person of the Lord and says: “One is my dove, my perfect one is but one, she is the only one of her mother, the chosen one of her that bore her.” Does he who does not hold this unity think that he holds the faith? Does he who strives against the Church and resists her think that he is in the Church, when too the blessed Apostle Paul teaches this same thing and sets forth the sacrament of unity saying: “One body and one Spirit, one hope of your calling, one Lord, one faith, one baptism, one God”?

Cyprian, The Unity of the Church 4