If one finishes his Salat wit Taslim after offering two or three Rak‘a (by mistake)

Narrated Abu Huraira:

The Prophet led us in the 'Asr or the Zuhr prayer and finished it with Taslim. Dhul-Yadain said to him, "O Allah's Apostle! Has the prayer been reduced?" The Prophet asked his companions in the affirmative. So Allah's Apostle I offered two more Rakat and then performed two prostrations (of Sahu). Sad said, "I saw that 'Ursa bin Az-Zubair had offered two Rakat in the Maghrib prayer and finished it with Taslim. He then talked (and when he was informed about it) he completed the rest of his prayer and performed two prostrations, and said, 'The Prophet prayed like this.' "

حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنْ سَعْدِ بْنِ إِبْرَاهِيمَ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ صَلَّى بِنَا النَّبِيُّ ﷺ الظُّهْرَ أَوِ الْعَصْرَ فَسَلَّمَ، فَقَالَ لَهُ ذُو الْيَدَيْنِ الصَّلاَةُ يَا رَسُولَ اللَّهَ أَنَقَصَتْ فَقَالَ النَّبِيُّ ﷺ لأَصْحَابِهِ " أَحَقٌّ مَا يَقُولُ ". قَالُوا نَعَمْ. فَصَلَّى رَكْعَتَيْنِ أُخْرَيَيْنِ ثُمَّ سَجَدَ سَجْدَتَيْنِ. قَالَ سَعْدٌ وَرَأَيْتُ عُرْوَةَ بْنَ الزُّبَيْرِ صَلَّى مِنَ الْمَغْرِبِ رَكْعَتَيْنِ فَسَلَّمَ وَتَكَلَّمَ ثُمَّ صَلَّى مَا بَقِيَ وَسَجَدَ سَجْدَتَيْنِ وَقَالَ هَكَذَا فَعَلَ النَّبِيُّ ﷺ.