i dont know the hadeeth but the following are the words of Imam Ghazali from Ihiya ul uloom Vol.III,P:36. Who has the right to argue in controversial matters..? " it is the duty of people after accepting Iman and Islam to engage themselves in worship and carry on their livelihood..and leave the ilmi masail at the hands of Ulema.. for a commoner to argue in these matters is more harmful and dangerous than Zina and stealing..since a person who is not well versed in deeni uloom and continues to argue in the masail of Allah and his deen.. it is very much possible that he forms an opinion thats is Kufr and he may not even be aware that what he thinks is kufr.. this is similar to a person who doesnt know swimming and jumps into the ocean." May Allah save us all.. wa assalam..