The Gospel entails persecution. The Gospel is that kind of a doctrine. Furthermore, the disciples of the Gospel are not all dependable. Many embrace the Gospel today and tomorrow discard it.
 Martin Luther, Commentary on the Epistle to the Galatians (1535). copy citation

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

Context

“But we can glory in the Lord and attend to our work cheerfully. Who cares whether our efforts please or displease the devil? Who cares whether the world praises or hates us? We go ahead "by honour and dishonour, by evil report and good report." (II Cor. 6:8.)
The Gospel entails persecution. The Gospel is that kind of a doctrine. Furthermore, the disciples of the Gospel are not all dependable. Many embrace the Gospel today and tomorrow discard it. To preach the Gospel for praise is bad business especially when people stop praising you. Find your praise in the testimony of a good conscience.
This passage may also be applied to other work besides the ministry.” source