Be what you would seem to be

Cf. [Aeschylus Seven against Thebes l. 592] οὐ γὰρ δοκɛῖν ἄρίσṯος ἀλἸ ɛἶναί θέλɛί, for he wishes not to appear but to be the best; [Sallust Catilina liv.] Esse, quam videri, bonus malebat, he [sc. Cato] preferred to be good, rather than to seem good.

Suche as thow semest in syghte, be in assay [trial] y-founde.
[c 1377 Langland Piers Plowman B. x. 253]

Be what thou wouldst seeme to be.
[1640 G. Herbert Outlandish Proverbs no. 724]

Be what you seem, and seem what you are. The best way! for Hypocrisy is soon discovered.
[1721 J. Kelly Scottish Proverbs 68]

It's a vegetable. It doesn't look like one, but it is. ‥the moral of that is—‘Be what you would seem to be.’
[1865 ‘L. Carroll’ Alice's Adventures in Wonderland ix.]

The Benningworth family motto Esse quam videri, ‘To be rather than to seem to be’.
[1980 G. Sims in H. Watson Winter Crimes 12 158]

Related to: appearance

Bibliography of major proverb collections and works cited from modern editions is available here.