Mishkat al-Masabih
Mishkat al-Masabih 78
Arabic hadith text
وَعَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ أَنَّ رَجُلًا سَأَلَهُ فَقَالَ: «إِنِّي أهم فِي صَلَاتي فيكثر ذَلِك عَليّ فَقَالَ الْقَاسِم بن مُحَمَّد امْضِ فِي صَلَاتك فَإِنَّهُ لن يذهب عَنْكَ حَتَّى تَنْصَرِفَ وَأَنْتَ تَقُولُ مَا أَتْمَمْتُ صَلَاتي» . رَوَاهُ مَالك
Translation
A man asked al-Qasim ibn Muhammad, “I become preoccupied during my prayer, and this happens to me repeatedly.” Al-Qasim ibn Muhammad replied, “Carry on with your prayer. It will not leave you until you finish and say, ‘I have not completed my prayer.’” Malik transmitted it.