“Forgetfulness in Prayer” is book 4 of Muwatta Malik, the collection of Imam Malik ibn Anas. It holds 3 hadiths — Hadith 222–224 in the standard numbering. Each is shown below in the original Arabic with an English translation, its full reference, and the grading the hadith scholars gave it where one was recorded.
Yahya related to me from Malik from Ibn Shihab from Abu Salama ibn Abdar-Rahman ibn Awf from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "When you stand in prayer, Shaytan comes to you and confuses you until you do not know how much you have prayed. If you find that happening do two sajdas from the sitting position
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِنِّي لأَنْسَى أَوْ أُنَسَّى لأَسُنَّ " .
Yahya related to me from Malik that he had heard that the Messenger of Allah, may Allah bless him and grant him peace, said, "I forget or I am made to forget so that I may establish the sunna
Yahya related to me from Malik that he had heard that a man questioned al-Qasim ibn Muhammad saying, "My imagination works in the prayer, and it happens to me a lot." Al-Qasim ibn Muhammad said, "Go on with your prayer, for it will not go away from you until you go away saying, 'I have not completed my prayer
Maqtu Daif· Salim al-Hilali
Text from the open hadith-api dataset. Hadith numbering follows that edition and can differ slightly from a printed copy — check the Arabic against a trusted mushaf of hadith before relying on a reference.