ENOfficial
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.
Source: sunnah.com
Other translations
Arabic
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
sunnah.com