وَقَالَ ٱلَّذِينَ كَفَرُوا لَوْلَا نُزِّلَ عَلَيْهِ ٱلْقُرْءَانُ جُمْلَةً وَٰحِدَةً ۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِۦ فُؤَادَكَ ۖ وَرَتَّلْنَـٰهُ تَرْتِيلًا

Waqala allatheena kafaroo lawlanuzzila AAalayhi alqur-anu jumlatan wahidatan kathalikalinuthabbita bihi fu-adaka warattalnahu tarteela

And those who disbelieve say, "Why was the Qur’ān not revealed to him all at once?" Thus [it is] that We may strengthen thereby your heart. And We have spaced it distinctly.