Rabanus Maurus

But this power of binding and loosing, though it seems given by the Lord to Peter alone, is indeed given also to the other Apostles, and is even now in the^ Bishops and Presbyters in every Church. (vid. Matt. 18:18.) But Peter received in a special manner the keys of the kingdom of heaven, and a supremacy of judicial power, that all the faithful throughout the world might understand that all who in any manner separate themselves from the unity of the faith, or from communion with him, such should neither be able to be loosed from the bonds of sin, nor to enter the gate of the heavenly kingdom.