"The Messenger of Allah ﷺ forgot and said the taslim after two rak'ahs. Dhul-Shimalain said to him: 'Has the prayer been shortened or did you forget, O Messenger of Allah ﷺ?' The Messenger of Allah ﷺ said: 'Is Dhul-Yadain speaking the truth?' They said: "Yes." So the Messenger of Allah ﷺ stood up and completed the prayer." (Using translation from Nasāʾī 1229)
نَسِيَ رَسُولُ اللهِ ﷺ فَسَلَّمَ فِي سَجْدَتَيْنِ فَقَالَ لَهُ ذُو الشِّمَالَيْنِ أَقَصُرَتِ الصَّلَاةُ أَمْ نَسِيتَ يَا رَسُولَ اللهِ؟ قَالَ رَسُولُ اللهِ ﷺ «أَصَدَقَ ذُو الْيَدَيْنِ» قَالُوا نَعَمْ «فَقَامَ رَسُولُ اللهِ ﷺ فَأَتَمَّ الصَّلَاةَ»