Laudator Temporis Acti

William Cowper, The Poetical Works, ed. William Benham (London: Macmillan, 1908), p. 503, in a section of Translations from the Greek:

Art thou some individual of a kind
Long-lived by nature as the rook or hind?
Heap treasure, then; for if thy need be such,
Thou hast excuse, and scarce canst heap too much.
But man thou seem'st: clear therefore from thy breast
This lust of treasure -- folly at the best!
For why shouldst thou go wasted to the tomb,
To fatten with thy spoils thou know'st not whom?

Benham in his notes does not identify the Greek original. It's by Lucilius, from the Greek Anthology 11.389:

Εἰ μὲν ζῇς ἐλάφου ταναὸν χρόνον, ἠὲ κορώνης,
  συγγνώμη πλεῖστον πλοῦτον ἀγειρομένῳ·
εἰ δέ τις ἐσσὶ βροτῶν, οὒς αὐτίκα γῆρας ἰάπτει,
  μή σέ γ᾽ ἀπειρεσίων οἶστρος ἕλῃ κτεάνων·
μὴ σὺ μὲν ἀτλήτοισιν ἐν ἄλγεσι θυμὸν ὀλέσσῃς,
  χρήσωνται δ᾽ ἄλλοι σοῖς ἀγαθοῖς ἀπόνως.

Here is W.R. Paton's prose translation:

If thou livest the long years of a stag or crow thou mayest be pardoned for amassing great wealth, but if thou art one of mortal men, whom old age right soon assails, let not the furious desire of immeasurable possessions beset thee, lest thou destroy thy soul in insufferable torture and others use thy goods without toiling for them.

For more on this theme, see here.