Sayyiduna Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever attributes to me what I did not say, let him take a house in Hell. Whoever gives a fatwa without knowledge, its sin is upon him. And whoever gives his brother wrong advice, while knowing that the right course is something else, has betrayed him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20353