The apostles have preached the Gospel to us from the Lord Jesus Christ; Jesus Christ has done so from God. Christ therefore was sent forth by God, and the apostles by Christ. Both these appointments, then, were made in an orderly way, according to the will of God. Having therefore received their orders, and being fully assured by the resurrection of our Lord Jesus Christ, and established in the word of God, with full assurance of the Holy Ghost, they went forth proclaiming that the kingdom of God was at hand. And thus preaching through countries and cities, they appointed the first-fruits of their labours, having first proved them by the Spirit, to be bishops and deacons of those who should afterwards believe…Our apostles also knew, through our Lord Jesus Christ, and there would be strife on account of the office of the episcopate. For this reason, therefore, inasmuch as they had obtained a perfect fore-knowledge of this, they appointed those presbyters already mentioned, and afterwards gave instructions, that when these should fall asleep, other approved men should succeed them in their ministry.
St. Clement I – First Epistle to the Church at Corinth, Ch 42 & 44, A.D. 96