The Rules of Forgetfulness (Sahw) in Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 50
وَ رَوَى مُحَمَّدُ بْنُ مُسْلِمٍ عَنْ أَبِي جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ قَالَ: «إِذَا كَثُرَ عَلَيْكَ اَلسَّهْوُ فَدَعْهُ فَإِنَّهُ يُوشِكُ أَنْ يَدَعَكَ إِنَّمَا هُوَ مِنَ اَلشَّيْطَانِ.
Muhammad ibn Muslim narrated from Imam Muhammad ibn Ali Al-Baqir عليه السلام who said: "If you experience frequent distraction (waswasah), ignore it, for it will soon leave you. It is only from Satan”.
- Ṣaḥīḥ al-Faqīh, p. 45