Sunan an-Nasa'i, Volume 2, Book 11, Hadith 954 (DarusSalam) ⓘ

It was narrated that Uqbah bin Amr said: "I followed the Messenger of Allah when he was riding, and I placed my hand on his foot and said : O Messenger of Allah, teach me Surah Hud and Surah Yusuf. He said: 'You will never recite anything greater before Allah than: "Say: I seek refuge with (Allah), the Lord of the daybreak." And "Say: I seek refuge with (Allah) the Lord of mankind.'"

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ أَبِي عِمْرَانَ، أَسْلَمَ عَنْ عُقْبَةَ بْنِ عَامِرٍ، قَالَ اتَّبَعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم وَهُوَ رَاكِبٌ فَوَضَعْتُ يَدِي عَلَى قَدَمِهِ فَقُلْتُ أَقْرِئْنِي يَا رَسُولَ اللَّهِ سُورَةَ هُودٍ وَسُورَةَ يُوسُفَ ‏.‏ فَقَالَ ‏"‏ لَنْ تَقْرَأَ شَيْئًا أَبْلَغَ عِنْدَ اللَّهِ مِنْ ‏{‏ قُلْ أَعُوذُ بِرَبِّ الْفَلَقِ ‏}‏ وَ ‏{‏ قُلْ أَعُوذُ بِرَبِّ النَّاسِ ‏}‏ ‏"‏ ‏.‏