Sufyan Thawri says: My father asked Abu Amr Shaybani about the saying of the Messenger of Allah, peace and blessings be upon him: "There is no deficiency in prayer." He said: This narration is as follows: "There is no deficiency in prayer." And the meaning of "no deficiency" is that a person should not leave the prayer in such a state that he even suspects that some part of his prayer remains; (he should leave) when he is certain that it is complete.
Hadith Referenceالفتح الربانی / أبواب الأذ كار الواردة عقب الصلاة / 1985
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«ترقیم بيت الأفكار الدولية: 9938»
Brief Explanation
Benefits: … In the authentic ahadith of this chapter, the following three scenarios regarding the two prostrations (sujood) of forgetfulness are mentioned:
(1) If the worshipper is in doubt about the number of rak‘ahs (units of prayer) and, due to being unable to make a definitive decision, bases his action on the lesser number, then he should perform the two prostrations before the salutation (salaam).
(2) If the worshipper is in doubt about the number of rak‘ahs, but in light of various indications he comes to a predominant assumption regarding a particular case, then he should perform the prostrations after the salutation.
(3) If, after the salutation, it becomes apparent that there was an addition, or such an omission for which repetition is not required, then the prostrations should be performed at that very moment, and then the salutation should be given again. (Bukhari, Muslim) For example, after giving the salutation, it is discovered that five rak‘ahs were performed, or the tashahhud was omitted. The remaining scenarios will be mentioned in the following chapters.