Augustine of Hippo

(Tr. xlvi. 5) Indeed he would not be an hireling, did he not receive wages from the hirer. (c. 6). Sons wait patiently for the eternal inheritance of their father; the hireling looks eagerly for the temporal wages from his hirer; and yet the tongues of both speak abroad the glory of Christ. The hireling hurteth, in that he doeth wrong, not in that he speaketh right: the grape bunch hangeth amid thorns; pluck the grape, avoid the thorn. Many that seek temporal advantages in the Church, preach Christ, and through them Christ’s voice is heard; and the sheep follow not the hireling, but the voice of the Shepherd heard through the hireling.