Deuteronomy 13:13-14

13Certain men, corrupt men, have gone out from among you, and have seduced the inhabitants of their city, saying, Let us go and serve other gods, which ye have not known;1 14Then shalt thou enquire, and make search, and ask diligently; and, behold, if it is truth, and the thing certain, that such abomination is wrought among you;