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.' "
Muwatta Malik Book 4, Hadith 3