عَنِ الْمُغِيرَةِ بْنِ شُعْبَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ أَمَّنَا رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فِي الظُّهْرِ أَوِ الْعَصْرِ فَقَامَ، فَقُلْنَا: سُبْحَانَ اللَّهِ، فَقَالَ: سُبْحَانَ اللَّهِ، وَأَشَارَ بِيَدِهِ يَعْنِي قُومُوا، فَقُمْنَا، فَلَمَّا فَرَغَ مِنْ صَلَاتِهِ سَجَدَ سَجْدَتَيْنِ، ثُمَّ قَالَ: ((إِذَا ذَكَرَ أَحَدُكُمْ قَبْلَ أَنْ يَسْتَتِمَّ قَائِمًا فَلْيَجْلِسْ وَإِذَا اسْتَتَمَّ قَائِمًا فَلَا يَجْلِسْ))
It is narrated from Sayyiduna Mughirah bin Shu’bah (may Allah be pleased with him), he says: The Messenger of Allah (peace and blessings be upon him) led us in the Zuhr or Asr prayer, and he stood up for the third rak‘ah (skipping the middle Tashahhud). When we said “Subhan Allah,” the Prophet (peace and blessings be upon him) also said “Subhan Allah” to alert us and gestured for us to stand, so we also stood up. When he was about to finish his prayer, the Prophet (peace and blessings be upon him) performed two prostrations and said: If anyone remembers before standing up completely straight, he should sit down, and if he has already stood up completely straight, then he should not sit down.