Laudator Temporis Acti

Erasmus, Adagia I x 59, in Collected Works of Erasmus, Vol. 32: Adages I vi 1 to I x 100, translated and annotated by R.A.B. Mynors (Toronto: University of Toronto Press, 1989), p. 260, with note on p. 381:

59 Aut mortuus est aut docet litteras
He must be either dead or teaching school

Ἤτοι τέθνηκεν ἢ διδάσκει γράμματα, He must be either dead or teaching school. An iambic line current as a proverb, and used in old days to convey that a man was in great misfortune, though it was not clear what he was doing. This passed into common speech, as Zenodotus tells us, on the following occasion. The Athenians, under command of Nicias, had on one occasion fought and lost a battle against the Sicilians; they suffered heavy casualties, and many prisoners were taken and carried off to Sicily, where they were compelled to teach Sicilian children their elements. And so the few who escaped and returned to Athens, when asked what so-and-so was doing in Sicily, used to reply with the line I have quoted above: 'He must be either dead or teaching school.'

59 Taken from Zenobius ('Zenodotus') 4.17. Thought to be a line from comedy (frag. adesp. 20 Kock). Zen. Ath. 1.43

The Latin:

Ἤτοι τέθνηκεν ἢ διδάσκει γράμματα, id est Aut periit aut profecto literas docet. Senarius prouerbialis, quo significabant olim cuipiam omnino male esse, tametsi parum liqueret, quid rerum ageret. Is autem hac occasione venit in vulgi sermonem autore Zenodoto. Athenienses duce Nicia parum feliciter aliquando pugnauerunt aduersus Siculos permultis occisis, plerisque captiuis in Siciliam abductis, qui Siculorum filios literas docere coacti sunt. Proinde pauci, qui fuga elapsi redierant Athenas, rogati quid hic aut ille faceret in Sicilia, modo memorato versiculo respondebant: Aut periit aut docet literas.