πυροῖς

From LSJ

ἐπέμψατε ἀγγέλους τοῖς ἀλλήλοις ὥστε ἔγνωτε τὸν κίνδυνον → you sent messengers to one another so that you knew the danger

Source

French (Bailly abrégé)

v. πῦρ.

Russian (Dvoretsky)

πῠροῖς: поэт. πῠροῖσι dat. pl. к πῦρ.