Sayyiduna Talhah bin Ubaydullah (may Allah be pleased with him) says that a man came to the Messenger of Allah (peace and blessings be upon him) and began asking about (the rulings of) Islam. the Messenger of Allah (peace and blessings be upon him) said: "Five prayers in the day and night (offer them)." He said: Is there any other prayer due from me besides these? He (peace and blessings be upon him) said: "No, but you may offer voluntary prayers."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2225