Mishkat al-Masabih #222

‘Amr b. Shu'aib quoted the authority of his father from his grandfather who said that the Prophet heard some people disagreeing about the Qur’an and said, “It was just on this account that your predecessors perished: they set parts of God’s Book against others, whereas God's Book was sent down only to be consistent; so do not use parts to falsify others. Speak about as much of it as you know, but where you are ignorant entrust it to him who knows.” Ahmad and Ibn Majah transmitted it.