Plautus, Bacchides, lines 816-7:
quem di diligunt / adulescens moritur
He whom the gods love / dies young
Menander, Dis Exapatōn (fourth century BCE), fragment quoted in Stobaeus (KT 111):
ὃν οἱ θεοὶ φιλοῦσιν, ἀποθνῄσκει νέος.
He whom the gods love, dies young.
Neither Dis Exapatōn nor Bacchides survives completely, but the fragments we have confirm that Plautus's work is directly based off Menander's. This line would seem to be a direct quotation.
The proverb is famous now in kind of a romantic way, but in context (in both plays) the meaning is the opposite: the clever slave is making a snarky comment about a gullible old man he's just defrauded, implying that his old age means the gods don't love him. Either way, it seems to be one of the more famous things Menander ever wrote, which is probably why Plautus translated it so directly.