صحيح مسلم

Anas (Allah be pleased with him) reported The Messenger of Allah (ﷺ) was observing prayer during Ramadan. I came and stood by his side. Then another man came and he stood likewise till we became a group. When the Messenger of Allah (ﷺ) perceived that we were behind him, he lightened the prayer. He then went to his abode and observed such (a long) prayer (the like of which) he never observed with us. When it was morning we said to him: Did you perceive us during the night? Upon this he said: Yes, it was this (realisation) that induced me to do that which I did. He (the narrator) said: The Messenger of Allah (ﷺ) began to observe Saum Wisal at the end of the month (of Ramadan), and some persons among his Companions began to observe this uninter- rupted fast, whereupon the Messenger of Allah (ﷺ) said: What about such persons who observe uninterrupted fasts? You are not like me. By Allah. if the month were lengthened for me, I would have observed Saum Wisal, so that those who act with an exaggeration would (have been obliged) to abandon their exaggeration.