صحیح ابن حبان
Ibn Hibban
كتاب الصوم
Book of Fasting
باب رؤية الهلال - ذكر البيان بأن المرء عليه إحصاء شعبان ثلاثين يوما ثم الصوم لرمضان بعده
Chapter on Sighting the Crescent - Clarifying that one should count thirty days of Sha’ban, then fast Ramadan
1 hadith
Hadith 3444
Sayyidah Aisha Siddiqa (may Allah be pleased with her) narrates: The Prophet Muhammad (peace and blessings be upon him) used to pay more attention to sighting the crescent of Sha'ban than to anything else. Then, upon sighting the crescent of Ramadan, he would begin to fast. If it was cloudy for the Prophet (peace and blessings be upon him), he would complete the count of thirty (30) days first, and then begin to fast.