How is prayer compensated for in the event of forgetfulness or error?

It has been established that the Prophet, peace and blessings be upon him, made mistakes in his prayer, and the prostration of forgetfulness (sujud (definition) al-sahw) was legislated to compensate for deficiencies resulting from additions, omissions, or doubts in prayer. Scholars have differed regarding the ruling on sujud al-sahw and its placement, and the madhhab (definition) of Imam Ahmad is considered to be the most closely adhering to what has been reported from the Prophet, peace and blessings be upon him.

According to Imam Ahmad, prostration (sujud) is divided into three categories: - Obligatory (Wajib (definition)): If the worshipper adds an extra bowing (ruku') or prostration (sujud), or if he says the taslim (definition) (salutation of peace) forgetfully before completing the prayer, or if he omits an obligatory part of the prayer, such as the first tashahhud (definition). In the case of intentional omission, the prayer becomes invalidated. - Sunnah (definition): If the worshipper utters a prescribed saying in an improper place. - Permissible (Mubah (definition)): If the worshipper omits a sunnah utterance, such as the opening supplication (du'a al-istiftah).

As for the placement of sujud al-sahw according to Imam Ahmad, it is generally before the taslim, except in two cases: if the worshipper says the taslim after a deficiency of one or more rak'ahs, or if the Imam bases his action on his dominant conjecture, in which case it is after the taslim. There is flexibility in this matter, so if one prostrates for all cases before or after the taslim, it is permissible.

It should be noted that sujud al-sahw does not compensate for omitting a pillar (rukn) or a condition (shart (definition)) of prayer; rather, it compensates for omitting obligatory (wajib) and sunnah acts.