25:32
وَ قَالَ ٱلَّذِينَ كَفَرُ وا۟ لَوْلَا نُزِّلَ عَلَيْ هِ ٱلْ قُرْءَانُ جُمْلَةً وَٰحِدَةً كَ ذَٰلِكَ لِ نُثَبِّتَ بِ هِۦ فُؤَادَ كَ وَ رَتَّلْ نَٰ هُ تَرْتِيلًا
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.
73:4
أَوْ زِدْ عَلَيْ هِ وَ رَتِّلِ ٱلْ قُرْءَانَ تَرْتِيلًا
Or add to it, and recite the Qur'an with measured recitation.