Isn’t he speaking entirely for our benefit? This was written for our benefit so that the person who plows or threshes should expect to receive a share of the crop.
Everything written long ago was written to teach us so that we would have confidence through the endurance and encouragement which the Scriptures give us.
All this is for your sake so that, as God’s kindness overflows in the lives of many people, it will produce even more thanksgiving to the glory of God.