Augustine of Hippo
Catena Aurea · Johannesevangelium 10
Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber. But he that entereth in by the door is the shepherd of the sheep. To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out. And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice. And a stranger will they not follow, but will flee from him: for they know not the voice of strangers. To Him the porter openeth.
(Tr. xlvi. 2) Or, the porter is our Lord Himself; for there is much less difference between a door and a porter, than between a door and a shepherd. And He has called Himself both the door and the shepherd. Why then not the door and the porter? He opens Himself, i. e. reveals1 Himself. If thou seek another person for porter, take the Holy Spirit, of whom our Lord below saith, He will guide you into all truth. (c. 16:13) The door is Christ, the Truth; who openeth the door, but He that will guide you into all Truth? Whomsoever thou understand here, beware that thou esteem not the porter greater than the door; for in our houses the porter ranks above the door, not the door above the porter.