The Messenger of Allah ﷺ used to take greater care in tracking the crescent of Shaban than he did with any other month. He would then fast upon sighting the crescent of Ramadan, and if it was obscured from him, he would count thirty days and then begin fasting.
كان رسول الله ﷺ يتحفظ من هلال شعبان ما لا يتحفظ من غيره، ثم يصوم لرؤية رمضان، فإن غم عليه، عد ثلاثين يوما ثم صام.
Narrated by Abu Dawud (2325), Imam Ahmad (25161), and Daraqutni (2149), who graded it sahih, as did Ibn Khuzayma (1910) and Ibn Hibban (3444), and Hakim (1/423) and from him Bayhaqi. All of them narrated it through Muawiya bin Salih Hadrami, from Abdullah bin Abu Qays, who said, "I heard Ayesha say" (and he mentioned it).Daraqutni said, "This chain is hasan sahih." Hakim said, "Sahih according to the criteria of the two Shaykhs." This is what he said, but Muawiya bin Salih Hadrami and Abdullah bin Abu Qays meet the criteria of Muslim alone.