(56) باب فِي صَوْمِ رَجَبَ
Narrated 'Uthman b. Hakim:
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.
Reference: Sunan Abi Dawud 2430
In-book reference: Book 14, Hadith 118
English translation: Book 13, Hadith 2424