Forgetfulness in Prayer

Narrated Abu Huraira:

The Prophet (ﷺ) led us in the `Asr or the Zuhr prayer and finished it with Taslim. Dhul-Yadain said to him, "O Allah's Messenger (ﷺ) ! Has the prayer been reduced?" The Prophet (ﷺ) asked his companions in the affirmative. So Allah's Messenger (ﷺ) I offered two more rak`at and then performed two prostrations (of Sahu). Sa`d said, "I saw that 'Urwa bin Az-Zubair had offered two rak`at 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 (ﷺ) prayed like this.' "