سنن ابن ماجه

It was narrated that 'Aishah said: "The Messenger of Allah (ﷺ) recited the following Verse: 'It is He Who has sent down to you (Muhammad) the Book (this Qur'an). In it are verses that are entirely clear, they are the foundations of the Book; and others not entirely clear (up to His saying: ) 'And none receive admonition except men of understanding.' Then he said: 'O 'Aishah, if you see those who dispute concerning it (the Qur'an), they are those whom Allah has referred to here, so beware of them.'"