Quran 25:32 from Surah Al-Furqaan on Divine Marvels.
وَقَالَ ٱلَّذِينَ كَفَرُواْ لَوۡلَا نُزِّلَ عَلَيۡهِ ٱلۡقُرۡءَانُ جُمۡلَةٗ وَٰحِدَةٗۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِۦ فُؤَادَكَۖ وَرَتَّلۡنَٰهُ تَرۡتِيلٗا
English translation: And said those who disbelieve Why not was revealed to him the Quran all at once all at once Thus that We may strengthen thereby your heart and We have recited it (with distinct) recitation
Transliteration: waqala alladhina kafaru lawla nuzzila alayhi al-qur'anu jum'latan wahidatan kadhalika linuthabbita bihi fuadaka warattalnahu tartilan