The Quran

114

أَفَغَيرَ اللَّهِ أَبتَغي حَكَمًا وَهُوَ الَّذي أَنزَلَ إِلَيكُمُ الكِتابَ مُفَصَّلًا ۚ وَالَّذينَ آتَيناهُمُ الكِتابَ يَعلَمونَ أَنَّهُ مُنَزَّلٌ مِن رَبِّكَ بِالحَقِّ ۖ فَلا تَكونَنَّ مِنَ المُمتَرينَ

Muhammad Asad

[say thou:] "Am I, then, to look unto anyone but God for judgment¹ [as to what is right and wrong], when it is He who has bestowed upon you from on high this divine writ, clearly spelling out the truth?"² And those unto whom We have vouchsafed revelation aforetime know that this one, too, has been bestowed from on high, step by step, by thy Sustainer.³ Be not, then, among the doubters -

Lit., "to seek a judge other than God".
The expression mufassalan could also be rendered as "in a manner that brings out the distinction (fail) between truth and falsehood" (Zamakhshari). The use of the plural "you" indicates that the divine writ is addressed to all who may come to know it.
See 2:146, and the corresponding note. The pronoun "it" may refer either to the earlier divine writ - the Bible - and to its prediction of the advent of a prophet descended from Abraham, or, more probably, to the Qur'an: in which case it must be rendered as "this one, too". In either case, the above phrase seems to allude to the instinctive (perhaps only subconscious) awareness of some of the followers of the Bible that the Qur'an is, in truth, an outcome of divine revelation.