Seeing the New Moon - Section 2 Mishkat al-Masabih 1975
Arabic hadith text
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أحصوا هِلَال شعْبَان لرمضان» . رَوَاهُ التِّرْمِذِيّ
Translation
He reported God’s messenger as saying, "Calculate on the basis of the new moon of Sha'ban when Ramadan begins." Tirmidhi transmitted it.