Mishkat al-Masabih 8 The Excellent Qualities of the Qur’an كتاب فضائل القرآن 91

وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «لَمْ يَفْقَهْ مَنْ قَرَأَ الْقُرْآنَ فِي أَقَلَّ مِنْ ثَلَاث» . رَوَاهُ التِّرْمِذِيّ وَأَبُو دَاوُد والدارمي

Abdallāh b. ‘Amr reported God’s messenger as saying, “The one who recites the Qur’ān in less than three nights does not understand it.” Tirmidhī, Abū Dāwūd and Dārimī transmitted it.