5 But the Lord mentioned three characters, and our duty is to search them out in the Gospel, that of the shepherd, the hireling, and the thief. I suppose you took notice when the lesson was being read, that He marked out the shepherd, the hireling, and the thief. “The Shepherd,” said He, “lays down His life for the sheep,” and enters in by the door. The thief and the robber, said He, go up by another way. “The hireling,” He said, if he sees a wolf or even a thief, “flees; because he cares not for the sheep;” for he is an hireling, not a shepherd.
The one enters in by the door, because he is the shepherd; the second goes up another way, because he is a thief; the third seeing them who wish to spoil the sheep fears and flees, because he is an hireling, because he cares not for the sheep; for he is an hireling. If we shall find these three characters, you have found, holy brethren, both those whom you should love, and those whom you should tolerate, and those of whom you must beware. The Shepherd is to be loved, the hireling is to be tolerated, of the robber must we beware.
There are men in the Church of whom the Apostle speaks, who preach the Gospel by occasion, seeking of men their own advantage, whether of money, or of honour, or human praise. They preach the Gospel, wishing to receive rewards in whatsoever way they can, and seek not so much his salvation to whom they preach, as their own advantage. But he who hears the word of salvation from him who has not salvation, if he believe Him whom he preaches, and put not his hope in him, by whom salvation is preached to him; he that preaches shall have loss; he to whom he preaches shall have gain.
Source: Sermons on Selected Lessons of the New Testament (New Advent)