"And those who disbelieve say: Why"—meaning, why—"is the Quran not sent down to him all at once?"—that is, just as it was sent down to Moses and to Jesus. Allah said: "Thus, that We may strengthen your heart with it, and We have recited it in a slow, rhythmic manner"—meaning, We have explained it clearly.
﴿وَقَالَ الَّذين كفرُوا لَوْلَا﴾ هلا ﴿نزل عَلَيْهِ الْقُرْآن جملَة وَاحِدَة﴾ أَيْ: كَمَا نَزَلَ عَلَى مُوسَى وَعَلَى عِيسَى، قَالَ اللَّهُ: ﴿كَذَلِكَ لِنُثَبِّتَ بِهِ فُؤَادَكَ وَرَتَّلْنَاهُ تَرْتِيلا﴾ يَعْنِي: وبيناه تبيينا.
