While the Prophet was in a Ghazwa he said, Some people have remained ...

Hadith 4:92

Narrated Anas:

While the Prophet 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. "