Hadith 12832

(حديث مرفوع) حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ ، عَنْ حُمَيْدٍ ، قَالَ : سُئِلَ أَنَسٌ عَنْ صَوْمِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ تَطَوُّعًا ، قَالَ : " كَانَ يَصُومُ حَتَّى نَقُولَ لَا يُفْطِرُ ، وَيُفْطِرُ حَتَّى نَقُولَ لَا يَصُومُ " .
Humaid says that someone asked Hazrat Anas (may Allah be pleased with him) about the voluntary fasts of the Prophet (peace and blessings be upon him), so he replied that the Prophet (peace and blessings be upon him) would sometimes fast continuously in a month to the extent that we would think that now the Prophet (peace and blessings be upon him) will not leave any fast, and sometimes he would leave fasting to the extent that we would say that perhaps now the Prophet (peace and blessings be upon him) will not fast at all.
Hadith Reference مسند احمد / مسند المكثرين من الصحابة / 12832
Hadith Grading حکم دارالسلام: إسناده صحيح، خ: 1141، م: 1158