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 يُونُسُ بْنُ عَبْدِ الأَعْلَى، قَالَ أَخْبَرَنِي أَنَسٌ، عَنْ سُهَيْلِ بْنِ أَبِي صَالِحٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ صَامَ يَوْمًا فِي سَبِيلِ اللَّهِ عَزَّ وَجَلَّ زَحْزَحَ اللَّهُ وَجْهَهُ عَنِ النَّارِ بِذَلِكَ الْيَوْمِ سَبْعِينَ خَرِيفًا " .
It was narrated from Abu Hurairah that the Messenger of Allah said: "Whoever fasts one day in the cause of Allah, the Mighty and sublime, Allah will remove his face away from the fire in return for the day (the distance of) seventy autumns.
Reference : Sunan an-Nasa'i 2244In-book reference : Book 22, Hadith 155English translation : Vol. 3, Book 22, Hadith 2246