It was narrated that Farwah bin Nawfal said:"I said to 'Aishah: 'Tell me of a supplication that the Messenger of Allah (ﷺ) used to say in his prayer.' She said: 'Yes. The Messenger of Allah (ﷺ) used to say: Allahumma inni author bika min sharri ma 'amiltu wa min sharri ma lam a'mal (O Allah, I seek refuge with You from the evil of that which I have done, and the evil of that which I have not done.)'"
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ هِلاَلِ بْنِ يِسَافٍ، عَنْ فَرْوَةَ بْنِ نَوْفَلٍ، قَالَ قُلْتُ لِعَائِشَةَ حَدِّثِينِي بِشَىْءٍ، كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَدْعُو بِهِ فِي صَلاَتِهِ . فَقَالَتْ نَعَمْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَقُولُ " اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنْ شَرِّ مَا عَمِلْتُ وَمِنْ شَرِّ مَا لَمْ أَعْمَلْ " .
Nesai
The Book of Forgetfulness (In Prayer) • Hadith 1307