Sayyiduna Ibn Umar (may Allah be pleased with them both) narrated that the Prophet Muhammad (peace and blessings be upon him) said: We are an unlettered nation; we neither write nor calculate. The month is like this and like this. He meant sometimes twenty-nine (days) and sometimes thirty (days). (He indicated with all his ten fingers three times.)
Hadith Referenceاللؤلؤ والمرجان / كتاب الصيام / 655
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 30 كتاب الصوم: 13 باب قول النبي صلی اللہ علیہ وسلم لا نكتب ولا نحسب»