Surah Al-Furqan 25:32

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

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.

Translation: Saheeh International

Tafsir

And those who disbelieve say ‘Why has the Qur’ān not been revealed to him all at once?’ as the Torah the Gospel and the Book of Psalms were. God exalted be He says We have revealed it thus in parts it is that We may strengthen your inner-heart with it and We have arranged it in a specific order that is to say We …

Excerpt from Tafsir al-Jalalayn, commentary on 25:32, via Quran.com. The reader has the full commentary and 9 more tafsirs.