Al-Adab Al-Mufrad #259

Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, "Anyone who attributes words to me which I did not say should take his seat in the Fire. Anyone who gives his Muslim brother misguided advice when they consult him has betrayed them. If anyone gives a fatwa which is not firm, the wrong action of that rests on the one who gave the fatwa."