Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "Do not go ahead of it" (the narrator says:) meaning, do not begin fasting before the month of Ramadan. "Begin fasting upon sighting it (that is, the new crescent), and if it is clouded over for you, complete the count of thirty."
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Ibn Ishaq, who is a mudallis (one who conceals defects in the chain), but he is thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 4806
Hadith Gradingمحدثین:إسنادہ حسن
Hadith Takhrij«أخرجه المعجم الأوسط للطبراني برقم: 6327»