Musannaf Ibn Abi Shayba 22:255

Ibn Numayr narrated to us, he said: Musa ibn Ubaydah narrated to us, he said: Abdullah ibn Yazid informed me, from Abd al-Rahman ibn Thawban, from Abdullah ibn Amr, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Leave off disputation regarding the Quran, for the nations before you were not cursed until they differed regarding the Quran. For disputation in the Quran is disbelief."