{A Book}, meaning: this is a Book, referring to the Quran, {which We have revealed to you}.
{People of understanding}, meaning: those possessing intellects, and they are the believers.
﴿كتاب﴾ أَي: هَذَا كتابٌ , يَعْنِي: الْقُرْآن ﴿أَنزَلْنَاهُ إِلَيْك﴾.
﴿أُوْلُو الأَلْبَابِ﴾ أَي: ذَوُو الْعُقُول وهم الْمُؤْمِنُونَ.
