Who said where there is life there is hope?

„While there is life there 's hope, he cried.“

—  John Gay English poet and playwright 1685 - 1732

Fable, The Sick Man and the Angel
Comparable to: "For the living there is hope, but for the dead there is none", Theocritus (3rd century BC), Idyl iv, 42; "Ægroto, dum anima est, spes est" ("While the sick man has life, there is hope", Cicero (1st century BC), Epistolarum ad Atticum, ix, 10
Fables (1727)

„While there's life there’s hope, and only the dead have none.“

—  Theocritus ancient greek poet

Idyll 4, line 42; translation by A. S. F. Gow, from Theocritus ([1950] 1952) vol. 1, p. 37.
Compare Cicero (1st century BC), Epistolarum ad Atticum [Epistle To Atticus], Book IX, 10, 4: Ægroto, dum anima est, spes est [While the sick man has life, there is hope.]
Idylls
Original: (el) τάχ᾽ αὔριον ἔσσετ᾽ ἄμεινον ἐλπίδες ἐν ζωοῖσιν, ἀνέλπιστοι δὲ θανόντες

„Holligsworth would have gone with me to the hither verge of life, and have sent his friendly and hopeful accents far over on the other side, while I should be treading the unknown path.“

—  Nathaniel Hawthorne, book The Blithedale Romance

The Blithedale Romance (1852)
Context: Hollingworth's more than brotherly attendance gave me inexpressible comfort. Most men - and certainly I could not always claim to be one of the exceptions - have a natural indifference, if not an absolute hostile feeling, towards those whose disease, or weakness, or calamity of any kind causes to falter or faint among the rude jostle of our existence. The education of Christianity, it is true, the sympathy of a like experience and the example of women, may soften and, possibly, subvert this ugly characteristic of our sex; but it is originally there, and has likewise its analogy in the practice of our brute brethren, who hunt the sick and disabled member of the herd from among them, as an enemy. It is for this reason that the stricken deer goes apart, and the sick lion grimly withdraws into his den. Except in love, or the attachments of kindred, or other very long and habitual affection, we really have no tenderness. But there was something of the woman moulded into the great, stalwart frame of Holligsworth; nor was he ashamed of it, as men often are of what is best in them, nor seemed ever to know that there was such a soft place in his heart. I knew it well, however, at that time, although afterwards it came nigh to be forgotten. Methought there could not be two such men alive as Holligsworth. There never was any blaze of a fireside that warmed and cheered me, in the down—sinkings and shiverings of my spirit, so effectually as did the light out of those eyes, which lay so deep and dark under his shaggy brows. Happy the man that has such a friend beside him when he comes to die!... How many men, I wonder, does one meet with in a lifetime, whom he would choose for his deathbed companions! It still impresses me as almost a matter of regret that I did not die then, when I had tolerably made up my mind to it; for Holligsworth would have gone with me to the hither verge of life, and have sent his friendly and hopeful accents far over on the other side, while I should be treading the unknown path.