الفرقان — Al-Furqan Ayat 32
وَقَالَ الَّذِيْنَ كَفَرُوْا لَوْلَا نُزِّلَ عَلَيْهِ الْقُرْاٰنُ جُمْلَةً وَّاحِدَةً ۛ كَذٰلِكَ ۛ لِنُثَبِّتَ بِهٖ فُؤَادَكَ وَرَتَّلْنٰهُ تَرْتِيْلًا
Wa qālal-lażīna kafarū lau lā nuzzila ‘alaihil-qur'ānu jumlataw wāḥidatan - każālika - linuṡabbita bihī fu'ādaka wa rattalnāhu tartīlā(n).
"And those who disbelieve say, "Why was the Qur'an not revealed to him all at once?" Thus [it is] that We may strengthen thereby your heart. And We have spaced it distinctly."