It wasnarrated from Qasim Abu 'Abdur-Rahman that he heard Mu'awiyahbinAbu Sufyan on the pulpit saying:
"The Messenger of Allah (ﷺ)usedto say from the pulpit, before the month of Ramadan: 'Fastingwillbegin on such and such a day, but we are going to start fastingearlier, so whoever wants to start fasting earlier (i.e., inSha'ban),let him do so, and whoever wants to wait until Ramadanbegins, let himdo so.'" (FR)
English reference (FR): Vol. 1, Book 7, Hadith 1647 (FR)
Arabic reference (FR): Book 7, Hadith 1716 (FR)