I heard 'A'isha (Allah be pleased with her) as saying: I had to complete some of the fasts of Ramadan, but I could not do it but during the month of Sha'ban due to my duties to the Messenger of Allah (ﷺ) or with the Messenger of Allah (ﷺ).
Sahih Muslim Book 13, Hadith 193
← Previous Hadith We, during the lifetime of the Messenger of Allah (ﷺ), in one month of Ramadan (observed fast according to our liking). He who wished to fast lasted and he who wished to break broke it and fed a needy person as an expiation 1544 till this verse was revealed:" He who witnesses among you the month (of Ramadan) he should observe fast during it" (ii. 184).

Sahih Muslim Book 13, Hadith 192 Next Hadith → This hadith is narrated on the authority of Yahya b. Sa'id with the same chain of transmitters but with this variation that he said that ('A'isha did not observe fast but in Sha'ban) out of regard for the Messenger of Allah (ﷺ).

Sahih Muslim Book 13, Hadith 194