"The person who knows one thing and does it better than anyone else, even if it only be the art of raising lentils, receives the crown he merits. If he raises all his energy to that end, he is a benefactor of mankind and its rewarded as such"

This quote is highlighting the significance of dedicating oneself to a particular skill or trade, and doing it remarkably well. The focus is on the idea that even the relatively little or ordinary tasks can be important and important to society, as long as they are finished with dedication and excellence. The term "receives the crown he benefits" indicates that this effort will be recognized and rewarded, personally and possibly also by others.