The Prophet ﷺ did not fast a complete month of the year except Shaban, which he would join to Ramadan.
عن النبي ﷺ أنه لم يكن يصوم من السنة شهرا تاما إلا شعبان يصله برمضان.
Abu Dawud (2336) narrated it from Imam Ahmad, and it is in his Musnad (26653) from Muhammad bin Jafar, who said, Shuba narrated to us, from Tawba Anbari, from Muhammad bin Ibrahim, from Abu Salama, from Umm Salama, and he related it. Bayhaqi (4/210) also narrated it by this route, and its isnad is sahih.Tirmidhi (736), Nasai (2175), and Imam Ahmad (26562) all narrated it through the route of Abdul-Rahman bin Mahdi, from Sufyan, from Mansur, from Salim bin Abu Jaad, from Abu Salama, from Umm Salama, who said, "I never saw the Messenger of Allah fast two consecutive months except that he used to join Shaban to Ramadan." Its isnad is also sahih, though Tirmidhi fell short in his judgment on it, saying, "The hadith of Umm Salama is a hasan hadith." He also narrated it in Shamail (295) with this isnad, saying, "This isnad is sahih." This latter judgment is more accurate than the first, unless the manuscript copies differ. Ibn Majah (1648) narrated it through another route from Shuba, from Mansur with his isnad, in abridged form.Tirmidhi noted that this hadith has also been narrated from Abu Salama, from Ayesha, that she said, "I never saw the Prophet fast more in any month than in Shaban. He used to fast all of it except a little, indeed he used to fast all of it." He then narrated it from Hannad, who said, Abda narrated to us, from Muhammad bin Amr, who said, Abu Salama narrated to us, from Ayesha, from the Prophet, to that effect. He said, "Salim Abu Nadr and others have also narrated from Abu Salama, from Ayesha, something similar to the narration of Muhammad bin Amr." End of quote.I say, the narration of Abu Nadr, from Abu Salama, from Ayesha, has already been mentioned above.