Definition of Doubt and Assumption and Their Rulings in Prayer

Question

In prayer, if you doubt the number of units, for example, in a two-unit prayer, but you think you are in the first unit, does that invalidate the prayer? Similarly, if there is an assumption after doubt in prayer, should I act based on the assumption? Or does it depend on the nature of the doubt and assumption?

Answer 1

Peace be upon you. **Ayatollah Khamenei (may Allah protect him):** Clarifications: - "Doubt" is the hesitation between two or more matters in such a way that none is preferred over the other. If one side has an advantage or is more likely than the other, the more likely side is called "assumption," and the weaker side is called "illusion." - If one doubts the number of units in prayer, such as whether they prayed three or four units, they should reflect for a moment. If they gain certainty or an assumption about one of the sides, they should act upon it, and their prayer is valid. Otherwise, they should follow the subsequent rulings. **Rulings on Doubt:** In two-unit and three-unit prayers, doubt about the number of units invalidates the prayer unless the doubt turns into an assumption, in which case they should act based on their assumption, and the prayer is valid. Source: [Message on Prayer and Fasting](https://www.leader.ir/ar/book/196/%D8%B1%D8%B3%D8%A7%D9%84%D8%A9-%D9%81%D9%8A-%D8%A7%D9%84%D8%B5%D9%84%D8%A7%D8%A9-%D9%88%D8%A7%D9%84%D8%B5%D9%88%D9%85?sn=31741) + [Doubt in Units](https://www.leader.ir/ar/book/196/%D8%B1%D8%B3%D8%A7%D9%84%D8%A9-%D9%81%D9%8A-%D8%A7%D9%84%D8%B5%D9%84%D8%A7%D8%A9-%D9%88%D8%A7%D9%84%D8%B5%D9%88%D9%85?sn=31744) + [Invalidating Doubts](https://www.leader.ir/ar/book/196/1?sn=31745) **Ayatollah Sistani (may Allah protect him):** Clarifications: - Doubt is the hesitation in a matter such that both possibilities are of concern to rational individuals. - Certainty is a strong assumption such that the opposing possibility is weak to the degree that rational individuals do not consider it in their affairs. - If the person praying doubts the number of units and their doubt is established, if it is in a two-unit, three-unit, or the first two of a four-unit prayer, it is invalid. - Assuming the units in obligatory prayer is like certainty, and likewise in voluntary prayer, it is obligatory to act upon it, meaning one cannot choose to assume fewer or more units. Thus, if your doubt turns into an assumption, you should act based on the assumption, and the prayer will not be invalidated. Source: [Definition of Some Terms in Fatwas](https://www.sistani.org/arabic/book/17/950/) + [Minhaj al-Salihin, Vol. 1, Doubt in the Number of Units of Obligatory Prayer](https://www.sistani.org/arabic/book/23720/4685/) May you be successful in all good.