Mukhtasar Bukhari (Abridged) 631 — If someone prays five rak‘ahs

Narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): The Messenger of Allah (peace and blessings of Allah be upon him) once offered five rak'ahs in the Zuhr prayer. After the prayer, it was said to him, "Has something been added to the prayer?" He (peace be upon him) said, "What do you mean?" It was said, "You have performed five rak'ahs." So after the salam, he (peace be upon him) performed two (prostrations of) forgetfulness (sahw).