Sahih Muslim
The Book of Fasting (Kitab Al-Sawm)
Book Number: 006 / Hadith Number: 2480
Abu Sa'id al-Khudri (Allah be pleased with him) reported: We went out on an expedition with the Messenger of Allah (may peace be upon him) during Ramadan. Some of us observed the fast and some of us broke it. Neither the observer of the fast had any grudge against one who broke it, nor the breaker of the fast had any grudge against one who had fasted They knew that he who had strength enough (to bear its rigour) fasted and that was good, and they also found that he who felt weakness (and could not bear the burden) broke it, and that was also good.