Rules of Doubt in Prayers

Important terminology

Certainty (yaqin): to know something without any doubt (100% certainty something is true). It is obligatory for a person to act according to their own certainty in fulfilling religious obligations.
Contentment (itminan): to be very confident about the reality of something but not to the extent of certitude (e.g., 95% sure). Contentment is acted upon as though acting on certainty; hence, it is obligatory to act according to one’s own contentment in fulfilling religious obligations.
Assumption of high likelihood (dhan): the preponderance of something being true (e.g., 70% certainty) over its opposite (30%). It is like certainty from the perspective of religious obligation in that it must be acted upon in some cases.
Doubt (shak): the uncertainty about something with two equally possible opposite states (50/50) with neither of them being more appropriate than the other.

Doubts that must be dismissed

Doubts about the prayer, a specific part of the prayer, or its required conditions if the doubt arises after the person has started the next part, after the time of fulfilling the condition, or after the prayer is completed: Examples include if the person doubts whether they recited Surat al-Fatihah during recitation of the second surah, doubts about their ruku when they are already descending towards sujud, doubts about sujud while in tashahhud, or doubts whether they performed asr prayer when the sun has already set. The doubts in all these cases must be dismissed. However, if the doubt occurs before entering the next part of the prayer, the person must perform the doubted act. For example, if a doubt arises about recitation of Surat al-Fatihah or the second surah before going to ruku, or doubts about performance of ruku before going to sujud, or doubts about performing sujud or tashahhud before starting the subsequent part, then they must complete the doubted part.
Doubt about correctly performing an act of prayer after completing it and before beginning the next part: For example, if a person doubts whether they recited a verse (ayah) of the surah correctly after having already recited it (i.e., they are reciting the next verse), they must dismiss such doubt.
An excessive doubter or one who suffers from wiswas (someone who obsesses over the proper fulfillment of acts such that it constantly hinders the performance of the salat) must dismiss their doubts.
An excessive doubter is one who doubts at least once every three prayers.
An excessive doubter should dismiss any doubts that arise, whether it is about the number of units (rakat), specific acts of salat, or its conditions. Their prayer is invalid if they pay heed to their doubt.^[i]
An excessive doubter is not required to use a counting method to keep track of their prayer or its acts.

Doubts that invalidate the prayer

The prayer becomes invalid if doubt leads to the person not knowing which unit (raka) they are performing.
If a person doubts the number of units (rakat) during fajr or maghrib, or in the first two units of a four-unit prayer (dhuhr, asr, or isha) then their prayer becomes invalid.

Dhan or assumption of high likelihood about the number of units

Any time a person has dhan or assumption of high likelihood about a unit (raka), they must follow their dhan and continue the prayer. For example, if a person is not sure what unit they are performing, but have dhan that it is the second, then the unit must be considered to be the second, so the person should continue the prayer, which would be considered valid.

Valid doubts about the number of units

Doubts about the number of units (rakat) are valid (i.e., must be redressed) if they occur after commencing the second sajdah in the second unit of a four-unit prayer.

In such cases, the person has two options:

Discontinue^[ii] the prayer and redo it if there is sufficient time remaining for its completion during the prescribed period. If discontinuing and redoing the prayer cannot be achieved within the prescribed time (e.g., redoing asr prayers when it is almost sunset), then it is not permissible to do so and the person must resort to the other option.
Apply one of the rulings related to the nine forms of doubts as detailed in the following table:

Type of Doubt	Part of Prayer	Ruling
(1) Whether 2^nd or 3^rd unit	After commencing the 2^nd prostration (sajdah) of the 2^nd unit	Must consider it the 3^rd unit and continue to the 4^th, and thereafter perform one-unit precautionary prayer (see below) in a standing position
(2) Whether 3^rd or 4^th unit	Any	Must consider it the 4^th unit and complete the prayer, and thereafter perform one-unit precautionary prayer in a standing position or two units in a sitting position
(3) Whether this is the 2^nd or 4^th unit	After commencing the last prostration	Must consider it the 4^th unit and complete the prayer, and thereafter perform two-units precautionary prayer in a standing position
(4) Whether 2^nd, 3^rd, or 4^th unit	After commencing the last prostration	Must consider it the 4^th unit and complete the prayer, and thereafter perform two-units precautionary prayer in a standing position followed by two units in a sitting position
(5) Whether 4^th or 5^th unit	After commencing the last prostration	Must consider it the 4^th unit and complete the prayer, and thereafter perform two prostrations of inadvertency (see below)
(6) Whether 4^th or 5^th unit	While standing	Must sit down immediately, consider it the 4^th unit, and complete the prayer, and thereafter perform one-unit precautionary prayer in a standing position
(7) Whether 3^rd or 5^th unit	While standing	Must sit down immediately, consider it the 4^th unit, and complete the prayer, and thereafter perform two-unit precautionary prayer in a standing position
(8) Whether 3^rd, 4^th, or 5^th unit	While standing	Must sit down immediately, consider it the 4^th unit, and complete the prayer, and thereafter perform two-unit precautionary prayer in a standing position followed by two units in a sitting position
(9) Whether 5^th or 6^th unit	While standing	Must sit down immediately, consider it the 4^th unit, and complete the prayer, and thereafter perform one-unit precautionary prayer in a standing position followed by two prostrations of inadvertency

Precautionary prayer (salat al-ihtiyat)

All the required conditions of prayer apply to the precautionary prayer, such as remaining in the state of purity throughout the prayer and not doing any of the acts that invalidate prayer.
The method of the precautionary prayer is as follows:

Fatihah must be recited under the breath, based on obligatory precaution, even if that precautionary prayer is being performed for a prayer in which the surahs must be recited aloud (e.g., maghrib prayer).
It is not obligatory to recite a second surah after Fatihah.
If something that invalidates prayer occurs (e.g., turning to the back) before the precautionary prayer, then based on obligatory precaution one must repeat the initial prayer, and there is no need to perform a precautionary prayer thereafter.

Making up forgotten parts

If during the prayer, a person forgets one prostration and then realizes it before commencing the subsequent pillar or rukn of prayer (e.g., ruku), then they must return and perform the single missed prostration and thereafter continue the rest of the prayer.
If the person realizes that they missed a prostration after commencing the subsequent pillar, then they must continue their prayer and immediately make up the prostration afterward.^[iii] Moreover, making up the single missed prostration does not require performance of tashahhud and taslim.
If the person forgets tashahhud during prayer and realizes it before commencing the subsequent pillar of prayer (e.g., ruku), they must immediately return to the seated position and perform tashahhud and thereafter continue the rest of the prayer. However, if they realize it after commencing the subsequent pillar, they must continue their prayer, and based on recommended precaution they should make up the tashahhud^[iv] immediately afterward.

Prostrations of inadvertency (sajdatay al-sahu)

It is obligatory to perform the two prostrations of inadvertency (sajdatay al-sahu) in the following cases:

Inadvertently speaking during prayer, based on obligatory precaution
Performing the salam (salutation) at a point during the prayer when one must not do so, based on obligatory precaution
When in doubt whether one is in the 4^th or 5^th unit or similar cases mentioned above
Forgetting to say tashahhud (testifying)
If the person realizes after completion of their prayer, that they have mistakenly omitted or added something, but they do not know specifically what was added or omitted, then they must perform the prostrations of inadvertency, based on obligatory precaution, even though their prayer is considered valid.

Method of prostrations of inadvertency

To perform the two prostrations of inadvertency, the person must make an intention to do so successively for the sake of nearness to Almighty God. Based on obligatory precaution, the prostrations should be performed on something that is permitted for prostration. After the second prostration, the person should say tashahhud followed by taslim.
Saying takbir (Allahu akbar) is not required, however, all the required conditions of prostration (as observed in the prayer) should be observed based on recommended precaution.
The person should say the following during prostration based on recommended precaution, “Bismillahi wa billah, assalamu alayka ayyuhan nabiyyu wa rahmatullahi wa barakatuh.”^[v]

^[i] If a person is a frequent doubter in a specific part of prayer, they must not pay heed to doubts regarding this specific part only.

^[ii] If the person chooses to discontinue the prayer, then they must perform one of the acts that invalidate prayers based on obligatory precaution, like turning their head to the back (i.e., away from qiblah).

^[iii] Based on obligatory precaution, the person must perform the prostration right after the prayer without doing any of the acts that invalidate prayer such as turning the head to the back.

^[iv] When making up the tashahhud it is not required to say salam afterwards.

^[v] “بِسْمِ اللهِ وَ بِاللهِ، اَلسَّلَامُ عَلَیْكَ أَيُّـهَا النَّبِيُّ وَ رَحْمَةُ اللهِ وَ بَـرَکَاتُهُ”.