поклясться
From LSJ
κράτιστοι δ᾽ ἂν τὴν ψυχὴν δικαίως κριθεῖεν οἱ τά τε δεινὰ καὶ ἡδέα σαφέστατα γιγνώσκοντες καὶ διὰ ταῦτα μὴ ἀποτρεπόμενοι ἐκ τῶν κινδύνων → the bravest are surely those who have the clearest vision of what is before them, glory and danger alike, and yet notwithstanding, go out to meet it | and they are most rightly reputed valiant who, though they perfectly apprehend both what is dangerous and what is easy, are never the more thereby diverted from adventuring
Russian > Greek
ἀποδίδωμι ὅρκον, βωμαίνω, διόμνυμι, διομνύναι, διόμνυσθαι, διομνύω, ἐνόμνυμαι, ἐπόμνυμι, ἐπομνύναι, κατόμνυμι, κατομνύναι, ὄμνυμι, ὀμνύναι, ὅρκον ἀποδιδόναι, ὁρκωμοτεῖν