ἢ λέγε τι σιγῆς κρεῖττον ἢ σιγὴν ἔχε → either say something better than silence or keep silence (Menander)
ἡσύχως, μαλακῶς, ἀμενηνόν, ἡσυχῆ, ἡσυχῇ, ἁσυχᾷ, ἠρέμα, ἦκα