Surah Al-Furqan
وَقَالَ ٱلَّذِينَ كَفَرُوا۟ لَوْلَا نُزِّلَ عَلَيْهِ ٱلْقُرْءَانُ جُمْلَةً وَٰحِدَةً ۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِۦ فُؤَادَكَ ۖ وَرَتَّلْنَـٰهُ تَرْتِيلًا
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.
📝 Footnotes
531) The Qur’an was not revealed all at once, but rather gradually in stages, so that the heart of Prophet Muhammad (may peace and blessings of Allah be upon him) would be strengthened and reassured.