Thus He made the Quran a muhaymin (guardian). A muhaymin is a witness, an arbiter, a trustee: it rules according to those parts of the previous Scriptures that Allah has not abrogated, and it bears witness to the truth of what remains in them, so long as it has not been altered. For this reason He said:
“Each community We have appointed a law and a clear way” (al-Maʾida 48).

This principle is firmly established in the authentic collections, the Sunan, and the Musnads. In the two Ṣaḥīḥs it is narrated from ʿAbd Allah ibn ʿUmar (may Allah be pleased with them both) that he said:

“The Jews came to the Messenger of Allah—may Allah bless him and grant him peace—and told him that a man and a woman among them had committed adultery. The Messenger of Allah—peace and blessings be upon him—said to them, ‘What do you find in the Torah regarding stoning?’ They replied, ‘We expose them publicly and flog them.’ ʿAbd Allah ibn Salām said, ‘You have lied; the Torah contains the ruling of stoning. Bring the Torah.’ They brought it, spread it open, and one of them placed his hand over the verse of stoning, reading what preceded it and what followed it. ʿAbd Allah ibn Salām said, ‘Lift your hand.’ When he lifted it, there was the verse of stoning. They said, ‘He has spoken the truth, O Muhammad.’ The Prophet—peace and blessings be upon him—then ordered that the two of them be stoned, and they were.”