Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
bayhaqi:8425[Chain 1] Abū Aḥmad ʿAbdullāh b. Muḥammad b. al-Ḥasan al-Mihrajānī And ʾAbū Naṣr Aḥmad b. ʿAlī al-Fāmī > Abū ʿAbdullāh Muḥammad b. Yaʿqūb > Ibrāhīm b. ʿAbdullāh > Muḥammad b. ʿUbayd > ʿUthmān b. Ḥakīm > Saʾalt Saʿīd b. Jubayr > Ṣawm Rajab Kayf Tará Fīh [Chain 2] Abū ʿAlī al-Rūdhbārī > Muḥammad b. Bakr > Abū Dāwud > Ibrāhīm b. Mūsá > ʿĪsá / Ibn Yūnus > ʿUthmān / Ibn Ḥakīm > Saʾalt Saʿīd b. Jubayr > Ṣiyām Rajab > Ibn ʿAbbās

[Machine] That the Messenger of Allah ﷺ used to fast so much that we would say he does not break his fast, and he would break his fast so much that we would say he does not fast.  

البيهقي:٨٤٢٥أَخْبَرَنَا أَبُو أَحْمَدَ عَبْدُ اللهِ بْنُ مُحَمَّدِ بْنِ الْحَسَنِ الْمِهْرَجَانِيُّ وَأَبُو نَصْرٍ أَحْمَدُ بْنُ عَلِيٍّ الْفَامِيُّ قَالَا ثنا أَبُو عَبْدِ اللهِ مُحَمَّدُ بْنُ يَعْقُوبَ ثنا إِبْرَاهِيمُ بْنُ عَبْدِ اللهِ ثنا مُحَمَّدُ بْنُ عُبَيْدٍ ثنا عُثْمَانُ بْنُ حَكِيمٍ قَالَ سَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ عَنْ صَوْمِ رَجَبٍ كَيْفَ تَرَى فِيهِ؟ ح وَأَخْبَرَنَا أَبُو عَلِيٍّ الرُّوذْبَارِيُّ أنبأ مُحَمَّدُ بْنُ بَكْرٍ ثنا أَبُو دَاوُدَ ثنا إِبْرَاهِيمُ بْنُ مُوسَى أنبأ عِيسَى يَعْنِي ابْنَ يُونُسَ ثنا عُثْمَانُ يَعْنِي ابْنَ حَكِيمٍ قَالَ سَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ عَنْ صِيَامِ رَجَبٍ فَقَالَ أَخْبَرَنِي ابْنُ عَبَّاسٍ

أَنَّ رَسُولَ اللهِ ﷺ كَانَ يَصُومُ حَتَّى نَقُولَ لَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لَا يَصُومُ  

رَوَاهُ مُسْلِمٌ فِي الصَّحِيحِ عَنْ إِبْرَاهِيمَ بْنِ مُوسَى

See similar narrations below:

Collected by Abū Dāwūd, Aḥmad
abudawud:2430Ibrāhīm b. Mūsá > ʿĪsá > ʿUthmān / Ibn Ḥakīm > Saʾalt Saʿīd b. Jubayr > Ṣiyām Rajab > Ibn ʿAbbās

I asked Sa'id b. Jubair about fasting during Rajab. He said: Ibn 'Abbas told me that the Messenger of Allah ﷺ used to fast to such an extent that we thought that he would never break his fast; and he would go without fasting to such an extent that we thought he would never fast.  

أبو داود:٢٤٣٠حَدَّثَنَا إِبْرَاهِيمُ بْنُ مُوسَى حَدَّثَنَا عِيسَى حَدَّثَنَا عُثْمَانُ يَعْنِي ابْنَ حَكِيمٍ قَالَ سَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ عَنْ صِيَامِ رَجَبَ فَقَالَ أَخْبَرَنِي ابْنُ عَبَّاسٍ

أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يَصُومُ حَتَّى نَقُولَ لاَ يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لاَ يَصُومُ  

ahmad:12832Yaḥyá b. Saʿīd > Ḥumayd > Suʾil Anas

I asked Sa'id b. Jubair about fasting during Rajab. He said: Ibn 'Abbas told me that the Messenger of Allah ﷺ used to fast to such an extent that we thought that he would never break his fast; and he would go without fasting to such an extent that we thought he would never fast. (Using translation from Abū Dāʾūd 2430)   

أحمد:١٢٨٣٢حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ عَنْ حُمَيْدٍ قَالَ سُئِلَ أَنَسٌ

عَنْ صَوْمِ رَسُولِ اللهِ ﷺ تَطَوُّعًا قَالَ كَانَ يَصُومُ حَتَّى نَقُولَ لَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لَا يَصُومُ  

ahmad:3009Muḥammad b. ʿUbayd > ʿUthmān b. Ḥakīm > Saʾalt Saʿīd b. Jubayr > Ṣawm Rajab Kayf Tará Fīh > Ibn ʿAbbās

I asked Sa'id b. Jubair about fasting during Rajab. He said: Ibn 'Abbas told me that the Messenger of Allah ﷺ used to fast to such an extent that we thought that he would never break his fast; and he would go without fasting to such an extent that we thought he would never fast. (Using translation from Abū Dāʾūd 2430)  

أحمد:٣٠٠٩حَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ حَدَّثَنَا عُثْمَانُ بْنُ حَكِيمٍ قَالَ سَأَلْتُ سَعِيدَ بْنَ جُبَيْرٍ عَنْ صَوْمِ رَجَبٍ كَيْفَ تَرَى فِيهِ؟ قَالَ حَدَّثَنِي ابْنُ عَبَّاسٍ

أَنَّ رَسُولَ اللهِ ﷺ كَانَ يَصُومُ حَتَّى نَقُولَ لَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لَا يَصُومُ