Rivers do not drink their own water; trees do not eat their own fruit. . . .

Rivers do not drink their own water; trees do not eat their own fruit; the sun does not shine on itself and flowers do not spread their fragrance for themselves. Living for others is a rule of nature. We are all born to help each other. No matter how difficult it is. . . . Life is good when you are happy; but much better when others are happy because of you.

And variants galore.

This has in recent times been widely attributed to Pope Francis, though I have yet to trace a use of it (or any version thereof) back to him.

Meanwhile its opening clauses antedate him by centuries, being unmistakably those of a Sanskrit subhāṣita present in the 14th-century Sūktiratnahāra (Sūkti ratna hāra). They ran in the Sūktiratnahāra as follows:

"Rivers do not drink their water; the trees do not eat [their own] fruits, the cloud never eats crops, [indeed] the lives of the virtuous are for the welfare of others."

This came into the 14th/18th-century Pali Lokanīti as follows:

"Rivers do not drink up their water, nor trees eat up their fruit; rain does not fall in some places only: the wealth of the virtuous is for others."

Source: Ujjwal Kumar, "Lokanīti: method of adaption and new vocabulary," Buddhist studies review 34, no. 1 (2017): 99 and elsewhere.

The Pali proverb in particular, at least, had made its way into the consciousness of English speakers by 1892 at the latest ("Rivers do not drink their own water; trees do not eat their own fruit; neither are clouds stationary anywhere. So also with wealth: it is for the benefit of others"). Indeed, by 1878. For the Burmese Lokanīti was first translated into English by Richard Carnac Temple in that year (Journal of the Asiatic Society of Bengal 47, no. 3 (1878)), and here it is: no. 23 on p. 247 ("The rivers drink not of their own water, neither eat the trees of their own fruit, nor fall the rains in every place: likewise are the riche of the jut man only for an help unto others"). And then again by James Gray in 1886 (no. 64 (Lokanīti) and no. 139 (Dhammanīti)):

"Rivers do not drink up their water, nor trees eat up their fruit; rain does not fall in some places only: the wealth of the virtuous is for others."

"Rivers do not drink up their water, nor trees eat up their own fruit; rain never eats up corn: the wealth of the righteous is for others."

Undoubtedly the variants on this have been legion. But IF Pope Francis "quoted" and adapted it (filling it out in the manner noted above, perhaps in imitation of someone else), I would be interested in knowing where, for, as I've just said, I have yet to identify a use of it by him. (He has, by the way, been notoriously sloppy on many occasions, and about matters far more serious than quotations.)