7. Once an act of worship has been completed, any later doubt has no effect. If, for example, someone finishes his wuḍūʾ and then wonders whether he rinsed his mouth; or ends the prayer and then questions whether he recited al-Fātiḥah, or whether he prostrated only once—he should pay no attention to such misgivings. The default assumption is that the act of worship is valid.

Ibn ʿAbd al-Qawī said:
"Post-completion doubt can never invalidate;
This rule extends to every act of devotion."