Sayyiduna Abdullah bin Sufyan al-Azdi (may Allah be pleased with him), who was a Companion of the Prophet (peace and blessings be upon him), narrated: Whoever fasts one day in the path of Allah, Allah Almighty removes that person from Hell by the distance of a hundred years. The narrator Habib asked Abu Bishr: "The distance of two hundred years?" Abu Bishr said to Aththamah bin Qays: "That is what I thought." Abdullah bin Sufyan said: "I will narrate to you the hadith I heard; I will not narrate to you what you narrate to me."
Imam al-Tabarani recorded it in al-Mu'jam al-Awsat, and something similar in al-Mu'jam al-Kabir. I do not know the narrator Abu Bishr; its remaining narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصيام / 5178