Sunan Abi Dawud, Hadith 2401

Narrated Jabir b. 'Abd Allah : The Prophet saw a man who had been put in the shade and saw a crowd of people around him (in the course of a journey). He said: Fasting while on journey is not part of righteousness.

حَدَّثَنَا أَبُو الْوَلِيدِ الطَّيَالِسِيُّ، حَدَّثَنَا شُعْبَةُ، عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ، - يَعْنِي ابْنَ سَعْدِ بْنِ زُرَارَةَ - عَنْ مُحَمَّدِ بْنِ عَمْرِو بْنِ حَسَنٍ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَأَى رَجُلاً يُظَلَّلُ عَلَيْهِ وَالزِّحَامُ عَلَيْهِ فَقَالَ ‏ "‏ لَيْسَ مِنَ الْبِرِّ الصِّيَامُ فِي السَّفَرِ ‏" ‏ ‏.‏

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also referenced under: Hadith 2407 (DarusSalam)