Gradual Revelation of Holy Quran
وَقَالَ الَّذِينَ كَفَرُوا لَوْلَا نُزِّلَ عَلَيْهِ الْقُرْآنُ جُمْلَةً وَاحِدَةً ۚ كَذَٰلِكَ لِنُثَبِّتَ بِهِ فُؤَادَكَ ۖ وَرَتَّلْنَاهُ تَرْتِيلًا {32}
And those who are committing Kufr say, ‘Why wasn’t the Quran Revealed unto him all at once?’ Like that, We Affirmed your heart with it, and We Arranged it (to be Revealed) gradually [25:32]