ENOfficial
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.
Source: sunnah.com
Other translations
Arabic
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
sunnah.com