Cyprian
Patristic
c. A.D. 200–258
“But that the Church is one, the Holy Spirit declares in the Song of Songs, saying, in the person of Christ, "My dove, my undefiled, is one; she is the only one of her mother, she is the choice one of her that bare her." Concerning which also He says again, "A garden enclosed is my sister, my spouse; a spring sealed up, a well of living water." But if the spouse of Christ, which is the Church, is a garden enclosed; a thing that is closed up cannot lie open to strangers and profane persons. And if it is a fountain sealed, he who, being placed without has no access to the spring, can neither drink thence nor be sealed. And the well also of living water, if it is one and the same within, he who is placed without cannot be quickened and sanctified from that water of which it is only granted to those who are within to make any use, or to drink.”