﴿ وَمَآ أَنزَلْنَا عَلَيْكَ ٱلْكِتَٰبَ إِلَّا لِتُبَيِّنَ لَهُمُ ٱلَّذِى ٱخْتَلَفُوا۟ فِيهِ ۙ وَهُدًۭى وَرَحْمَةًۭ لِّقَوْمٍۢ يُؤْمِنُونَ ﴾

“And upon thee [too] have We bestowed from on' high this divine writ for no other reason than that thou might make clear unto them all [questions of faith] on which they have come to hold divergent views, and [thus offer] guidance and grace unto people who will believe.”

Please check ayah 16:65 for complete tafsir.