Which one Church, also, the Holy Spirit in the Song of Songs, speaking in Our Lord’s name, says, “My dove, my spotless one, is but one. She is the only one of her mother, elect of her that bare her” (6:9). Does he who does not hold this unity of the Church think that he holds the faith? Does he who strives against and resists the Church trust that he is in the Church, when moreover the blessed Apostle Paul teaches the same thing, and sets forth the sacrament of unity, saying, “There is one body and one spirit, one hope of your calling; one Lord, one faith, one baptism, one God”? (Ephesians 4:5)....."
-St.Cyprian of Carthage, 251 A.D.