Language:
كتاب الجهاد والسير
56  
Fighting for the Cause of Allah (Jihaad)
(71)
Chapter: The service, during holy battles
(71)
باب فَضْلِ الْخِدْمَةِ فِي الْغَزْوِ
Sahih al-Bukhari 2890

Narrated Anas:

We were with the Prophet (on a journey) and the only shade one could have was the shade made by one's own garment. Those who fasted did not do any work and those who did not fast served the camels and brought the water on them and treated the sick and (wounded). So, the Prophet (ﷺ) said, "Today, those who were not fasting took (all) the reward."

حَدَّثَنَا سُلَيْمَانُ بْنُ دَاوُدَ أَبُو الرَّبِيعِ، عَنْ إِسْمَاعِيلَ بْنِ زَكَرِيَّاءَ، حَدَّثَنَا عَاصِمٌ، عَنْ مُوَرِّقٍ الْعِجْلِيِّ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم أَكْثَرُنَا ظِلاًّ الَّذِي يَسْتَظِلُّ بِكِسَائِهِ، وَأَمَّا الَّذِينَ صَامُوا فَلَمْ يَعْمَلُوا شَيْئًا، وَأَمَّا الَّذِينَ أَفْطَرُوا فَبَعَثُوا الرِّكَابَ وَامْتَهَنُوا وَعَالَجُوا فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ ذَهَبَ الْمُفْطِرُونَ الْيَوْمَ بِالأَجْرِ ‏"‏‏.‏
Reference : Sahih al-Bukhari 2890
In-book reference : Book 56, Hadith 105
USC-MSA web (English) reference : Vol. 4, Book 52, Hadith 140
  (deprecated numbering scheme)