ἀφρὸν καχλάζειν

From LSJ

μηδενὶ συμφορὰν ὀνειδίσῃς, κοινὴ γὰρ ἡ τύχη καὶ τὸ μέλλον ἀόρατον → never mock a disaster, fate is common to all and the future unknown

Source

Greek > English (Woodhouse)

burst forth into foam, burst into froth