The Book of Fasting
22/44. Chapter:
The Reward of one who fasts one day in the cause of Allah, The Mighty And Sublime, And Mentioning The Differences Reported From Suhail Bin Abi Salih In The Narration About That
Sunan an-Nasai
أَخْبَرَنَا الْحَسَنُ بْنُ قَزَعَةَ، عَنْ حُمَيْدِ بْنِ الأَسْوَدِ، قَالَ حَدَّثَنَا سُهَيْلٌ، عَنِ النُّعْمَانِ بْنِ أَبِي عَيَّاشٍ، قَالَ سَمِعْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ صَامَ يَوْمًا فِي سَبِيلِ اللَّهِ عَزَّ وَجَلَّ بَاعَدَهُ اللَّهُ عَنِ النَّارِ سَبْعِينَ خَرِيفًا " .
It was narrated that An-Numan bin Abi 'Ayyash said: "I heard Abu Saeed Al-Khudri say: 'The Messenger of Allah said: Whoever fasts one day in the cause of Allah will separate his face from the fire by (a distance of) seventy autumns."'
Reference : Sunan an-Nasa'i 2249In-book reference : Book 22, Hadith 160English translation : Vol. 3, Book 22, Hadith 2251