Surah Al-Furqan, ayah 32

وَقَالَ ٱلَّذِينَ كَفَرُواْ لَوۡلَا نُزِّلَ عَلَيۡهِ ٱلۡقُرۡءَانُ جُمۡلَةٗ وَٰحِدَةٗۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِۦ فُؤَادَكَۖ وَرَتَّلۡنَٰهُ تَرۡتِيلٗا ٣٢

Waqālal-ladhīna kafarū lawlā nuzzila 'alayhil-qur'ānu jumlatan wāhidatan kadhālika linuthabbita bihī fu'ādaka warattalnāhu tartīlā

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.¹⁰²³