From Hesiod’s Works and Days (361-2) but lifted from Plutarch, who quotes it in both How A Man May Become Aware of his Progress in Virtue and The Education of Children (twice, I think, though only once via quote). I used to be much interested in the reception of Hesiod in the Second Sophistic – more the use of him as historic figure than of his poetry – but never so much with Plutarch, partly because his inclusion in the movement can be hazy.
For if you put down even a little upon a little and do this often, then this too will quickly become a lot
εἰ γάρ κεν καὶ σμικρὸν ἐπὶ σμικρῷ καταθεῖο,
καὶ θαμὰ τοῦτ᾽ ἔρδοις, τάχα κεν μέγα καὶ τὸ γένοιτο.