From the scholia to Aristophanes, Ecclesiazusae 751, where the headword phrase - effectively meaning 'No deal on the strength of a mere promise' -- occurs. See also the fuller omicron 805; and cf. Anecdota graeca, ed. L. Bachmann, 322.2; Photius, Lexicon s.v. (but without a gloss).
[1] For this idiom see also alpha 463, alpha 571, alpha 1193, alpha 2108, alpha 2220, alpha 4308, alpha 4538, epsilon 2406, epsiloniota 66, epsiloniota 78, iota 172, kappa 1272, mu 768, mu 922, omicron 975, sigma 643, sigma 974, upsilon 528; and cf. epsilon 3344.