Salim bin Abdullah narrates from his father (Sayyiduna Abdullah bin Umar, may Allah be pleased with them both), who narrates from Sayyiduna Umar (may Allah be pleased with him), that the Prophet Muhammad (peace and blessings be upon him) said: "Whoever is following the Imam (in prayer), it is not obligatory upon him to perform the prostration of forgetfulness (sajdah sahw) due to his own mistake. But if the Imam makes a mistake, then it is obligatory upon the Imam to perform sajdah sahw, and it is also obligatory upon those praying behind him. However, if someone praying behind the Imam makes a mistake, then sajdah sahw is not obligatory upon him; rather, the Imam suffices for him."

Salim bin Abdullah narrates from his father that the Prophet Muhammad (peace be upon him) said: "Sajdah Sahw (prostration of forgetfulness) in prayer becomes obligatory only when a person stands instead of sitting or sits instead of standing."

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: Once Sayyiduna Umar (may Allah be pleased with him) was discussing with me about making a mistake in prayer. During this, Sayyiduna Abdur Rahman bin Awf (may Allah be pleased with him) came to us. He came and stayed with us. He said: I heard the Prophet (peace and blessings of Allah be upon him) say: "If a person has doubt about his prayer, then he should perform so much prayer that his doubt becomes about having added to the prayer."

Ubaidullah bin Abdullah (narrates this statement of Sayyiduna Abdullah bin Abbas, may Allah be pleased with them): Once I was present with Sayyiduna Umar, may Allah be pleased with him, and we were discussing about prayer. During this, Sayyiduna Abdur Rahman bin Auf, may Allah be pleased with him, arrived. He said: Shall I not narrate to you the hadith which I heard from the Messenger of Allah, peace and blessings be upon him? I heard the Messenger of Allah, peace and blessings be upon him, say: "When you have doubt about any deficiency during prayer, then continue performing the prayer until that doubt becomes about an addition."