Deuteronomy 13:13-14

13Certain base fellows are gone out from the midst of thee, and have drawn away the inhabitants of their city, saying, Let us go and serve other gods, which ye have not known;

14then shalt thou inquire, and make search, and ask diligently; and, behold, if it be truth, and the thing certain, that such abomination is wrought in the midst of thee;