Sunan an-Nasa’i 2090
The Book of Fasting
The Obligation of Fasting
It was narrated from Talhah bin 'Ubaidullah that: a Bedouin came to the Messenger of Allah with unkempt hair and said: "O Allah has enjoined upon me of Salah." He said: "The five daily prayers, unless you do any more voluntarily." He said: "Tell me what Allah has enjoined upon me voluntarily." He said: "Tell me what Allah has enjoined upon me of fasting." He said: "Fasting the month of Ramadan, unless you do any more voluntarily." He said: "Tell me what Allah has enjoined upon me of Zakah." The Messenger of Allah told him of the laws of Islam, He said: "By the One Who has honored you, I will not do anything voluntarily, and I will not do anything voluntarily, and I will not do less than that which Allah has enjoined upon, me: The Messenger of Allah said: "He will succeed if he is sincere," or "He will enter Paradise if he is sincere."