Ali bin Sahl al-Ramli said: I asked Imam al-Shafi'i (may Allah have mercy on him) about the Qur'an, and he said: It is the speech of Allah; it is not created. I asked: What is the ruling, in your view, on one who says it is created? He said: He is a disbeliever. I said to Imam al-Shafi'i (may Allah have mercy on him): What is the view of your teachers? He said: They say the same: those who say the Qur'an is created are disbelievers.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20894