Surah 3:7
"He (it is) who has sent down on you the Book, of which some verses are clearly composed – they are the mother of the Book – but others are ambiguous. As for those in whose hearts (there is) a turning aside, they follow the ambiguous part of it, seeking (to cause) trouble and seeking its interpretation. No one knows its interpretation except God. And (as for) the ones firmly grounded in knowledge, they say, ‘We believe in it. All (of it) is from our Lord.’ Yet no one takes heed except those with understanding."
– some verses are clearly composed . . . but others are ambiguous
The Quran seems to say that one part of “the book” is ambiguous, causing some to seek interpretation for the ambiguous verses. This verse says that no one knows the interpretation of the ambiguous part except Allah.
The expression “mother of the Book” appears here and at 13.39 and 43.4. It seems to refer to a concept of an original book in heaven from which all revelation comes. See the discussion of the “doctrine of scripture” within the Quran at 85.21–22.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam