وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ
قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أحصوا هِلَال شعْبَان لرمضان»
He reported God’s messenger as saying, “Calculate on the basis of the new moon of Shaban when Ramadan begins.”
Mishkat al-Masabih 1885, Book 8, Fasting, Hadith 19. 1 min read