Let him desire to do good work and to preach the Gospel in all its purity. Whether an ungrateful world appreciates his efforts is to give him no concern because, after all, he is in the ministry not for his own glory but for the glory of Christ.
 Martin Luther, Commentary on the Epistle to the Galatians (1535). copy citation

add
Author Martin Luther
Source Commentary on the Epistle to the Galatians
Topic purity ministry
Date 1535
Language English
Reference
Note Translated by Theodore Graebner
Weblink http://www.gutenberg.org/files/1549/1549-h/1549-h.htm

Context

“In this artful manner they hoodwink the people who rather enjoy to see their former pastors taken down a few notches by such upstarts.
"Let a minister be faithful in his office," is the apostolic injunction. "Let him not seek his own glory or look for praise. Let him desire to do good work and to preach the Gospel in all its purity. Whether an ungrateful world appreciates his efforts is to give him no concern because, after all, he is in the ministry not for his own glory but for the glory of Christ. A faithful minister cares little what people think of him, as long as his conscience approves of him. The approval of his own good conscience is the best praise a minister can have. To know that we have taught the Word of God and administered the sacraments rightly is to have a glory that cannot be taken away.
source