The cases, that require two prostrations (sajdah) of inadvertence (sajdat al-sahw

A.      Talking absent-mindedly during prayer.

B.       Doubting the number of unit (rak’ah), e.g., whether they are in the fourth or fifth unit (rak`ah) of prayer, after finishing the second prostration (sajdah);

C.      Forgetting to say the testament of faith (tashahhud);

In the following two cases, it is required to perform two prostrations as per obligatory precaution:

A.    Forgetting one prostration (sajdah).

B.     Absent-mindedly uttering the concluding salutation (salām) of prayer at the wrong time.

Ayatollah Sistani: In two cases, after giving salām at the end of the prayer, a person must perform two prostrations of forgetfulness (sajdat al-sahw) in the manner that will be explained later:

1. If one completely forgets the tashahhud.
2. In a four-rakʿah prayer, if after entering the second sajdah one doubts whether four rakʿahs have been performed or five, or doubts whether four rakʿahs have been performed or six, just as mentioned in the fourth case of the valid doubts.

And in three cases based on obligatory precaution (iḥtiyāṭ wājib) sajdat al-sahw is required:

1. If one knows in a general way that something was mistakenly omitted from or added to the prayer, while the prayer itself is judged to be valid.
2. If one speaks unintentionally during the prayer.
3. If one gives the salām of the prayer at a place where it should not be given, for example, unintentionally giving salām in the first rakʿah.

It is recommended (iḥtiyāṭ mustaḥabb) that if one forgets a single sajdah or sits where one should be standing—such as sitting while reciting Sūrat al-Ḥamd and the second sūrah by mistake—or stands where one should be sitting—such as standing instead of sitting for tashahhud—then two prostrations of forgetfulness should be performed. Rather, it is recommended to perform two prostrations of forgetfulness for anything that is mistakenly omitted from or added to the prayer.

Ayatollah Makarem Shirazi: For several matters, based on obligatory precaution, two prostrations of forgetfulness must be performed after the prayer in the prescribed manner:

1. Improper speech: that is, speaking unintentionally while thinking that the prayer has ended.
2. Improper salām: for example, giving salām in the second rakʿah of a four-rakʿah prayer.
3. A forgotten sajdah.
4. A forgotten tashahhud.
5. Sitting instead of standing unintentionally or standing instead of sitting.
6. In the doubt between four and five rakʿahs after the second sajdah, it is obligatory to complete the prayer and then perform two prostrations of forgetfulness afterward.

Speaking Inadvertently

Ayatollah Sistani: If a person speaks by mistake, or thinking that their prayer has finished, they must—as a precaution—perform two sajdat al-sahw.

Ayatollah Makarem Shirazi: Sajdat al-sahw is not obligatory for the sound that comes from coughing; but if a person forgetfully groans, sighs (“āh”/a moan), or says “āh,” then—based on obligatory precaution (iḥtiyāṭ wājib)—they must perform sajdat al-sahw.

1.      If one pronounces a word incorrectly and then repeats it correctly, it is not obligatory to perform two prostrations (sajdah) of inadvertence for reciting it again.

2.      If one unintentionally says several words in prayer, but all of them are considered as one speech, two prostrations (sajdah) of inadvertence are sufficient.

Improper Salām (Salām Given in the Wrong Place)

Ayatollah Sistani: If a person mistakenly gives the salām of the prayer in a place where it should not be given, and says “al-salāmu ʿalaynā wa ʿalā ʿibādillāh al-ṣāliḥīn”, or says “al-salāmu ʿalaykum”—even if they do not add “wa raḥmatullāhi wa barakātuh”—then, based on obligatory precaution (iḥtiyāṭ lāzim), they must perform two prostrations of forgetfulness (sajdat al-sahw). However, if they mistakenly say “al-salāmu ʿalayka ayyuhā al-nabī wa raḥmatullāhi wa barakātuh”, then it is recommended (iḥtiyāṭ mustaḥabb) to perform two sajdat al-sahw.

But if they utter two letters or more from the salām (other than the above), then based on obligatory precaution, they must perform two sajdat al-sahw.

Ayatollah Makarem Shirazi: If a person mistakenly says “al-salāmu ʿalayka ayyuhā al-nabī wa raḥmatullāhi wa barakātuh”, sajdat al-sahw is not obligatory, rather recommended.

But if they say any part of the other two forms of salām, then based on obligatory precaution, they must perform two prostrations of forgetfulness.

A Forgotten Prostration (Sajdah) or Testament of Faith (Tashahhud)

2.  Ayatollah Sistani: If a person forgets one sajdah or the tashahhud, and remembers it before the rukūʿ of the next rakʿah, they must go back and perform it. Then, after the prayer, it is recommended precaution (iḥtiyāṭ mustaḥabb) to perform two prostrations of forgetfulness (sajdat al-sahw) for the extra standing (standing in a place where one should not have stood).

Method of performing Prostration (Sajdah) of Inadvertence

بسم الله وبالله السلام علیك أیها النبي ورحمة الله وبرکاته

One must repeat it twice and then recite the testament of faith (tashahhud) and the concluding salutation [salām].

Ayatollah Sistani: The method of performing the prostrations of forgetfulness (sajdat al-sahw) is as follows: immediately after giving salām at the end of the prayer, one should intend to perform sajdat al-sahw and—based on obligatory precaution—place the forehead on something on which prostration is valid. It is recommended as a precaution to recite a dhikr during it, and it is better to say: “Bismillāh wa billāh, al-salāmu ʿalayka ayyuhā al-nabī wa raḥmatullāhi wa barakātuh.”Then one should sit, go down into prostration again, recite the same dhikr, and sit up again. After that, one should recite the tashahhud and say: “Al-salāmu ʿalaykum,”and it is preferable to add: “wa raḥmatullāhi wa barakātuh.”

Ayatollah Makarem Shirazi: Immediately after giving salām at the end of the prayer, one should intend to perform sajdat al-sahw and place the forehead on something on which prostration is valid, and say: “Bismillāh wa billāh, al-salāmu ʿalayka ayyuhā al-nabī wa raḥmatullāhi wa barakātuh.”

Then one should raise the head from prostration and sit, go down into prostration again and recite the same dhikr. After lifting the head from the second prostration, one should sit, recite the tashahhud, and give salām. As a precaution, it is sufficient in the tashahhud to recite only the obligatory amount, and to suffice with only the final salām.

Redressing the Forgotten (Qaḍā’) Prostration (Sajdah) or Testament of Faith (Tashahhud)