Hesiod W&D 361-362: The straw that broke the camel's back

εἰ γάρ κεν καὶ σμικρὸν ἐπὶ σμικρῷ καταθεῖο,
καὶ θαμὰ τοῦτ' ἔρδοις, τάχα κεν μέγα καὶ τὸ γένοιτο

For if you place a small thing upon a small thing, and you do this often, soon it will become large.