Tertullian

“ And yet you will be bound so to defend that presumption, as to deny that the (points) which you think applicable to Christians are referable to a heathen. Tell me, is not all mankind one flock of God? Is not the same God both Lord and Shepherd of the universal nations? [5] Who more “perishes” from God than the heathen, so long as he “errs?” Who is more “re-sought” by God than the heathen, when he is recalled by Christ? ”

“ When, in reply to this, the Lord had figured the restoration of the lost ewe, to whom else is it credible that he configured it but to the lost heathen, about whom the question was then in hand,—not about a Christian, who up to that time had no existence? Else, what kind of (hypothesis) is it that the Lord, like a quibbler in answering, omitting the present subject-matter which it was His duty to refute, should spend His labour about one yet future? “But a ‘sheep’ properly means a Christian, [2] and the Lord’s ‘flock’ is the people of the Church, [3] and the ‘good shepherd’ is Christ ”

“ No sooner has (such a) man made his appearance than he is expelled from the Church; nor does he remain there; nor does he cause joy to the Church which discovers him, but grief; nor does he invite the congratulation of her neighbours, but the fellowship in sadness of the surrounding fraternities. ”