It was narrated from Saeed bin Abi Hind that Mutarrif a man from Banu 'Amir bin Sa'sa'ah told him that:'Uthman bin Abi Al-As called for milk to be given to him (Mutarrif) to drink. Mutarrif said: 'I heard the Messenger of Allah say: 'Fasting is a shield like the shield of any one of you in battle."' Abu Hurairah said: "The Messenger of Allah said: 'Fasting is a shield."' (Sahih
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ سَعِيدِ بْنِ أَبِي هِنْدٍ، أَنَّ مُطَرِّفًا، - رَجُلٌ مِنْ بَنِي عَامِرِ بْنِ صَعْصَعَةَ - حَدَّثَهُ أَنَّ عُثْمَانَ بْنَ أَبِي الْعَاصِ دَعَا لَهُ بِلَبَنٍ لِيَسْقِيَهُ فَقَالَ مُطَرِّفٌ إِنِّي صَائِمٌ فَقَالَ عُثْمَانُ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " الصِّيَامُ جُنَّةٌ كَجُنَّةِ أَحَدِكُمْ مِنَ الْقِتَالِ " .
Nesai
The Book of Fasting • Hadith 2230