From Sahih Bukhari (Hadith 2839):
Narrated Anas:While the Prophet (ﷺ) was in a Ghazwa he said, "Some people have remained behind us in Medina and we never crossed a mountain path or a valley, but they were with us (i.e. sharing the reward with us), as they have been held back by a (legal) excuse
Reference: Bukhari 2839