Original quote from Herodotus, The Histories (8.111): "(2)...for the men of that place, the first islanders of whom Themistocles demanded money, would not give it. When, however, Themistocles gave them to understand that the Athenians had come with two great gods to aid them, Persuasion and Necessity, and that the Andrians must therefore certainly give money, they said in response, “It is then but reasonable that Athens is great and prosperous, being blessed with serviceable gods."
Herodotus is quoted by Plutarch in Themistocles (21.1): he said he came escorting two gods, Persuasion and Compulsion. (Greek: "δύο γὰρ ἥκειν ἔφη θεοὺς κομίζων, Πειθὼ καὶ Βίαν")
NOTE the two different sets of "gods" in the Original Greek: πειθώ τε καὶ ἀναγκαίην (Herodotus); Πειθὼ καὶ Βίαν (Plutarch)