The Lord had said, “Thou shalt have none other gods but Me.” A prophet is here supposed who invites the people “to go after other gods.” To such a one no credit is under any circumstances to be given, even should he show signs and wonders to authenticate his doctrine. The standing rule of faith and practice had been laid down once for all - that the people were to hold fast. The prophet who propounded another rule could only be an impostor.
A different case is considered in Deuteronomy 18:18, etc.