It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: We are an unlettered nation; we neither know how to write nor how to calculate. The month is of such and such days, and such and such days, and such and such days. The third time, the Prophet (peace and blessings be upon him) folded his thumb (i.e., indicating 29 days). Then he said: The month is of such and such days, and such and such days, and such and such days, meaning a complete (30) days.
Hadith Referenceالفتح الربانی / كتاب الصيام / 3684
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«اخرجه البخاري: 1913، ومسلم: 1080 ، (انظر مسند أحمد ترقيم الرسالة: 5017 ترقیم بيت الأفكار الدولية: 5017»
Brief Explanation
Benefits: … The Prophet sallallahu alayhi wa sallam was indicating the number ten by spreading open the fingers of both hands.