The words "piety with contentment" do not mean piety with the possession of a sufficient quantity of necessities, although this meaning may also be allowed. Rather, they mean piety with the feeling of contentment, when piety so fills a man's heart that, according to its spirit, he feels content.
"Those men, the teachers of another doctrine and disputants, wrongly suppose that piety is gain" (Blessed Theophylact), "because they hypocritically clothe themselves in the garment of piety, so as to have in it a means for acquisition" (Oecumenius).
"There is gain in piety, but not as they suppose. It is far higher. In it there is gain not when one has possessions, but when one has none, for it teaches contentment. Contentment is great and lasting wealth" (Blessed Theophylact).
"Piety, then, is in itself a true acquisition, because it is content with what exists and does not seek excess. Or one may understand it this way: piety is gain because with it men do not seek abundance, but are satisfied with having enough of what is necessary" (Oecumenius).
Thus the spirit of piety, by making a man content and therefore rich, extinguishes the thirst for acquisitions. Yet natural reasoning can lead everyone to the same point. What sense is there in spending care and labor on this, when you will take nothing away from here with you?