This narration is reported by Muhammad ibn Ahmad ibn Yahya, from ‘Abbad ibn Sulayman, from Sa‘d ibn Sa‘d, from Muhammad ibn al-Qasim ibn Fudayl ibn Yasar, from al-Hasan ibn al-Jahm, who said: I asked Abu al-Hasan عليه السلام about a man who prayed Dhuhr or ‘Asr and invalidated his wudu after sitting in the fourth rak‘ah. Imam عليه السلام said: 'If he had already recited Ashhadu an la ilaha illa Allah سبحانه وتعالى wa anna Muhammadan Rasul Allah سبحانه وتعالى (the testimony of faith) before invalidating his wudu, then he does not need to repeat the prayer. However, if he had not recited the testimony of faith before invalidating his wudu, then he must repeat the prayer.'"