οἱ Κάδμου πόλιν τεκνοῦσι παίδων παισί

From LSJ

οὔ τι τὰ πολλὰ ἔπη φρονίμην ἀπεφήνατο δόξαν → a multitude of words is no proof of a prudent mind, many words do not declare an understanding heart

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