St Gregory the Theologian, Bishop of Nazianzus
Worthy of faith is every [priest] (called) to purify thee, if only he be of the number of those who have received authority for this, who are not manifestly condemned and not alienated from the Church. Thou, who requirest treatment, judge not the judges, look not into the worthiness of those cleansing thee, make not a selection, looking at the parents. Even if one is better and another lower, still every one is higher than thee. Reason thus: there are two rings - one of gold and one of iron - and on both is engraved one and the same royal countenance, and by both are wax seals made. In what way does one seal differ from the other? In no way. Identify the material on the wax, if thou art wiser than everyone; tell which impression is from the iron ring and which from the gold ring? And why are they identical? For although the material is different, but there is no difference in the seals. So too may every [priest] be a baptizer for thee, for even though one surpasses another by his life, but the force of Baptism is equal, and every [priest] who is instructed in the same faith can equally bring thee to perfection.
St John Chrysostom
It happens that laymen live in piety, while priests live in unrighteousness, and therefore, if grace were to seek everywhere only the worthy, neither Baptism nor the offering of the Body of Christ ought to be performed through them. But now the Lord usually acts even through the unworthy, and the grace of Baptism is not in the least injured by the life of the priest. I say this so that anyone strictly examining the life of a priest would not begin to be tempted, reasoning about what he performs in the Sacraments. For a man does not introduce anything from himself, but all this is the work of God's power, and God sanctifies you in the Sacraments.