Sahih Muslim , Book 6, Hadith 2585 (USC-MSA) ⓘ

'Uthman b. Hakim al-Ansari said: I asked Sa'id b. Jubair about fasting In Rajab, and we were then passing through the month of Rajab, whereupon he said: I heard Ibn 'Abbas (Allah be pleased with both of them) as saying: The Messenger of Allah used to observe fast (so continuously) that we (were inclined) to say that he would not break (them) and did not observe them so conti- nuously) that we (were inclined to say) that he would not observe fast.

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ، ح وَحَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا عُثْمَانُ بْنُ حَكِيمٍ الأَنْصَارِيُّ، قَالَ سَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ عَنْ صَوْمِ، رَجَبٍ - وَنَحْنُ يَوْمَئِذٍ فِي رَجَبٍ - فَقَالَ سَمِعْتُ ابْنَ عَبَّاسٍ - رضى الله عنهما - يَقُولُ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُ حَتَّى نَقُولَ لاَ يُفْطِرُ ‏.‏ وَيُفْطِرُ حَتَّى نَقُولَ لاَ يَصُومُ ‏.‏