Ἄμεινόν ἐστιν σιωπᾶν καὶ εἶναι, ἢ λαλοῦντα μὴ εἶναι. καλὸν τὸ διδάσκειν, ἐὰν ὁ λέγων ποιῇ.
It is better for a man to be silent and be [a Christian], than to talk and not to be one. It is good to teach, if he who speaks also acts.
Ignatius of Antioch – early Christian Greek clergyman and church father, around 68-100 Bishop of Antioch (died around 110), from the letter to the Ephesians attributed to him, chapter 15:1