Calvin (Institutes 4.10.26) quotes Augustine as saying that “even hirelings are needful” in the church.
But I think he must be right.
In John 10, Jesus contrasts the good shepherd to the hired hand, or “hireling”:
I am the good shepherd; the good shepherd lays down His life for the sheep. He who is a hired hand, and not a shepherd, who is not the owner of the sheep, sees the wolf coming, and leaves the sheep and flees, and the wolf snatches them and scatters them. He flees because he is a hired hand and is not concerned about the sheep.
– John 10:11-13 NASB
Here’s Augustine on this passage:
But give heed to the fact that even the hirelings are needful. For many indeed in the Church are following after earthly profit, and yet preach Christ, and through them is heard the voice of Christ; and the sheep follow, not the hireling, but the Shepherd’s voice speaking through the hireling. Hearken to the hirelings as pointed out by the Lord Himself: “The scribes,” He saith, “and the Pharisees sit in Moses’ seat: do what they say; but do not what they do.” (Matt. xxiii. 2, 3). What else said He but, Listen to the Shepherd’s voice speaking through the hirelings? For sitting in Moses’ seat, they teach the law of God; therefore God teacheth by them. But if they wish to teach their own things, hear them not, do them not. For certainly such seek their own, not the things which are Jesus Christ’s; but no hireling has dared to say to Christ’s people, Seek your own, not the things which are Jesus Christ’s. For his own evil conduct he does not preach from the seat of Christ: he does injury by the evil that he does, not by the good that he says.
–Augustine, Homilies on the Gospel of John, Chapter X. 11–13, point 6.
Witness the majesty of our God in His mysterious and good care of His elect. O come, let us adore Him!