"Let me, therfore, most earnestly recommend to you, to hoard up, while you can, a great stock of knowledge; for though, during the dissipation of your youth, you may not have occasion to spend much of it; yet, you may depend upon it, that a time will come, when you will want it to maintain you. Public granaries are filled in plentiful years; not that it is known that the next, or the second, or the third year will prove a scarce one; but because it is known that, sooner or later, such a year will come, in which the grain will be wanted."
— Stanhope, Philip Dormer, fourth earl of Chesterfield (1694-1773)
(I.lxxx, p. 239 [pp. 42-3 in Roberts ed.], BATH, October 4, O.S. 1746)
Reading David Roberts' edition of Lord Chesterfield's Letters (Oxford: OUP, 1998); and searching text from Project Gutenberg <Link>
Consulting and citing, where possible, Letters Written by the late Right Honourable Philip Dormer Stanhope, Earl of Chesterfield, to his son, Philip Stanhope, Esq. (London: Printed for J. Dodsley, 1774). <Link to ECCO>
See also Miscellaneous Works of the late Philip Dormer Stanhope, Earl of Chesterfield: Consisting of letters to his Friends, never before printed, and Various Other Articles. 2 vols. (London: Printed for Edward and Charles Dilly, 1777). <Link to ECCO>