صحیح ابن حبان
Ibn Hibban
كتاب الصوم
Book of Fasting
باب رؤية الهلال - ذكر الأمر بالقدر لشهر شعبان إذا غم على الناس رؤية هلال رمضان
Chapter on Sighting the Crescent - Command to estimate the month of Sha’ban if the crescent of Ramadan is obscured
1 hadith
Hadith 3441
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: I heard the Prophet Muhammad (peace and blessings be upon him) say: "When you see it, then fast; when you see it, then celebrate Eid al-Fitr. If clouds cover it from you, then complete the counting."