ἐχθές
ἔγνω δὲ φώρ τε φῶρα καὶ λύκος λύκον → the thief knows the thief and the wolf knows the wolf, and thief knows thief and wolf his fellow wolf, set a thief to catch a thief
English (LSJ)
Adv.
A = χθές, yesterday, Ar.Nu.175, Th.616, etc.; ἀπ' ἐ. AP 11.35 (Phld.); μέσφα τό γ' ἐ. Theoc.2.144; οὐ γάρ τι νῦν γε κἀ. today or yesterday, S.Ant.456; οὐκ ἐ. οὐδὲ πρῴην Antipho Fr.58; ἐ. καὶ τρίτης [ἡμέρας] LXX Ru.2.11, cf. M.Ant.10.7. (ἐχθές is commoner than χθές in Com. and LXX, is the only form used in NT, and freq. in papyri of all periods, PSI4.442.21 (iii B.C.), etc.; cf. χθές.)
German (Pape)
[Seite 1124] = χθές, gestern, Ar. Nubb. 175; οὐ νῦν τε κἀχθές, ἀλλ' ἀεί Soph. Ant. 452; τὰ ἐχθὲς καὶ πρώην γεγονότα Plat. Gorg. 470 d; Xen. Cyr. 7, 5, 53 u. öfter, Nach Apollon. in B. A. 556, 30 soll χθές attischer sein, es ist wenigstens häufiger.