63. Nicodemus enquires about regeneration, and the Lord replies: “Verily, verily, I say unto thee, except a man be born again by water and the Spirit, he cannot enter into the kingdom of God.” And that He might show that there is one birth according to the flesh, and another according to the Spirit, He added: “That which is born of the flesh is flesh, because it is born of the flesh; and that which is born of the Spirit is Spirit, because the Spirit is God.”4 Follow out the whole course of the passage, and you will find that God has shut out your impiety by the fulness of His statement: “Marvel not,” says He, “that I said, Ye must be born again. The Spirit breatheth where He listeth, and thou hearest His voice, but knowest not whence He cometh or whither He goeth, so is every one who is born of the Spirit.”
Ambrose of Milan, “Three Books of St. Ambrose on the Holy Spirit,” in St. Ambrose: Select Works and Letters, ed. Philip Schaff and Henry Wace, trans. H. de Romestin, E. de Romestin, and H. T. F. Duckworth, vol. 10, A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, Second Series (New York: Christian Literature Company, 1896), 144.