Narrated Abdullah ibn Amr ibn al-'As: Wahb ibn Munabbih said: Abdullah ibn Amr asked the Prophet (ﷺ); In how many days should one complete the recitation of the Qur'an? He said: In forty days. He then said: In one month. He again said: In twenty days. He then said: In fifteen days. He then said: In ten days. Finally he said: In seven days.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا نُوحُ بْنُ حَبِيبٍ، أَخْبَرَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ سِمَاكِ بْنِ الْفَضْلِ، عَنْ وَهْبِ بْنِ مُنَبِّهٍ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، أَنَّهُ سَأَلَ النَّبِيَّ صلى الله عليه وسلم فِي كَمْ يَقْرَأُ الْقُرْآنَ قَالَ " فِي أَرْبَعِينَ يَوْمًا " . ثُمَّ قَالَ " فِي شَهْرٍ " . ثُمَّ قَالَ " فِي عِشْرِينَ " . ثُمَّ قَالَ " فِي خَمْسَ عَشْرَةَ " . ثُمَّ قَالَ " فِي عَشْرٍ " . ثُمَّ قَالَ " فِي سَبْعٍ " . لَمْ يَنْزِلْ مِنْ سَبْعٍ .
sunnah.com