Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2348 (DarusSalam) ⓘ

It was narrated that Ibn 'Abbas said: "The Messenger of Allah would fast until we said he would not break his fast, and he would not fast until we said he does not want to fast. And he never fasted any month in full apart from Ramadan, from the time he came to Al-Madinah."

أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا مُحَمَّدٌ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُ حَتَّى نَقُولَ لاَ يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ مَا يُرِيدُ أَنْ يَصُومَ وَمَا صَامَ شَهْرًا مُتَتَابِعًا غَيْرَ رَمَضَانَ مُنْذُ قَدِمَ الْمَدِينَةَ ‏.‏