It is narrated from Hazrat Abdullah that the Noble Prophet (peace and blessings be upon him) once led the Zuhr prayer with five rak‘ahs. It was said to him, "Did you pray five rak‘ahs?" So after the salam, the Prophet (peace and blessings be upon him) performed two prostrations. And (Imam) Abu Hanifa's opinion is mentioned that: If one does not sit for the tashahhud in the fourth rak‘ah, he must repeat the prayer.