Hadith 5:107
Abu Umama reported God’s messenger as saying, "If anyone fasts for a day while on jihad ,* God will put between him and hell a ditch as wide as the distance between heaven and earth." * Mirqat gives this meaning, but says it may refer to the hajj , the 'umra , seeking knowledge, or desiring to please God. The Arabic is 'in God’s way.' Tirmidhi transmitted it.
وَعَنْ أَبِي أُمَامَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ صَامَ يَوْمًا فِي سَبِيلِ اللَّهِ جَعَلَ اللَّهُ بَيْنَهُ وَبَيْنَ النَّارِ خَنْدَقًا كَمَا بَيْنَ السَّمَاءِ وَالْأَرْضِ» . رَوَاهُ التِّرْمِذِيّ
Original Reference: Mishkat al-Masabih 2064