Sayyiduna Talhah bin Ubaydullah (may Allah be pleased with him) says: A man with dishevelled hair came to the Messenger of Allah (peace and blessings be upon him) and said: O Messenger of Allah, tell me how many prayers Allah has made obligatory upon me. He (peace and blessings be upon him) said: "The five prayers, unless you wish to perform some voluntary prayers." Then he said: Tell me how many fasts Allah Almighty has made obligatory upon me. He (peace and blessings be upon him) said: "The fasts of the month of Ramadan, unless you wish to observe some voluntary fasts." Then he said: Tell me how Allah Almighty has made zakah obligatory upon me. So the Messenger of Allah (peace and blessings be upon him) informed him of the essential rites of Islam. He said: By the One who has honoured you (peace and blessings be upon him)! I will not perform any voluntary worship, nor will I ever fall short in the obligations. the Messenger of Allah (peace and blessings be upon him) said: "This man has succeeded if he has spoken the truth," and "he has entered Paradise, by Allah, if he has spoken the truth."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7903