Sahih Muslim
The Book of Fasting (Kitab Al-Sawm)
Book Number: 006 / Hadith Number: 2455
'A'isha reported that a person came to the Apottle of Allah (may peace be upon him) asking for a fatwa (religious verdict). She ('A'isha) had been overhearing it from behind the curtain. 'A'isha added that he (the person) had said: Messenger of Allah, (the time) of prayer overtakes me as I am in a state of junub; should I observe fast (in this state)? Upon this the Messenger of Allah (may peace be upon him) said: (At times the time) of prayer overtakes me while I am in a state of junub, and I observe fast (in that very state), whereupon he said: Messenger of Allah, you are not like us Allah has pardoned all your sins, the previous ones and the later ones. Upon this he (the Holy Prophet) said: By Allah, I hope I am the most God-fearirg of you, and possess the best knowledge among you of those (things) against which I should guard.