swear by

From LSJ

καὶ ποιήσας φραγέλλιον ἐκ σχοινίων πάντας ἐξέβαλεν ἐκ τοῦ ἱεροῦ, τά τε πρόβατα καὶ τοὺς βόας → And having made a whip out of cords he drove all from the temple sheep and cattle

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