At-Tawbah 9:120 ما كان لاهل المدينة ومن حولهم من الاعراب ان يتخلفوا عن رسول الله ولا يرغبوا بانفسهم عن نفسه ذالك بانهم لا يصيبهم ظما ولا نصب ولا مخمصة في سبيل الله ولا يطيون موطيا يغيظ الكفار ولا ينالون من عدو نيلا الا كتب لهم به عمل صالح ان الله لا يضيع اجر المحسنين ١٢٠

It was not (permissible) for the people of Madīnah and for those around them of the Bedouins to stay behind abandoning the Messenger of Allah, nor to prefer their own lives to his life. That is because whatever thirst or fatigue or hunger strikes them in the way of Allah, and whenever they step into a place which infuriates the infidels, and whenever they make a gain from an enemy, a virtuous deed is credited to their account. Surely, Allah does not nullify the reward of the virtuous.