“He who receives a benefit with gratitude, repays the first installment of it.”

I like a broadly hypothesized scope of an overall observation. Does the benefit derive from a contract (agreed to formal obligation), a gift (how does one correspondingly if fact, repay a gift) or ...? OR, does identifying an original source even matter? 

Consider Grace as the benefit, from mercy bestowed. Gratitude indeed. 

I get it, and agree!