The Prophet ﷺ said (to ʿAbdullah), "Fast three days a month." ʿAbdullah said, (to the Prophet) "I am able to fast more than that." They kept on arguing on this matter till the Prophet ﷺ said, "Fast on alternate days, and recite the whole Qur'an once a month." ʿAbdullah said, "I can recite more (in a month)," and the argument went on till the Prophet ﷺ said, "Recite the Qur'an once each three days." (i.e. you must not recite the whole Qur'an in less than three days). (Using translation from Bukhārī 1978)
عَنِ النَّبِيِّ ﷺ قَالَ «صُمْ مِنَ الشَّهْرِ ثَلَاثَةَ أَيَّامٍ» قَالَ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ قَالَ فَمَا زَالَ حَتَّى قَالَ «صُمْ يَوْمًا وَأَفْطِرْ يَوْمًا» وَقَالَ «اقْرَأِ الْقُرْآنَ فِي شَهْرٍ» فَقُلْتُ إِنِّي أُطِيقُ أَكْثَرَ مِنْ ذَلِكَ حَتَّى قَالَ «اقْرَأِ الْقُرْآنَ فِي ثَلَاثٍ»