λαμβάνειν τῆς φιλίας πεῖράν
From LSJ
πολλὰ μεταξὺ πέλει κύλικος καὶ χείλεος ἄκρου → there is many a slip twixt cup and lip, there's many a slip twixt cup and lip, there's many a slip 'twixt cup and lip, there's many a slip twixt the cup and the lip, there's many a slip 'twixt the cup and the lip
make proof of some one's friendship