The Messenger of Allah ﷺ said, "Whoever fasts a single day in the cause of Allah , Allah will distance Hellfire from him by a journey of a hundred years."
عن رسول الله ﷺ قال: من صام يوما في سبيل الله عز وجل باعد الله منه جهنم مسيرة مائة عام.
Narrated by Nasai (2254), Ibn Abu Asim in Kitab al-Jihad (169), and Tabarani in Kabir (17/335), all from the hadith of Muhammad bin Shuayb, who said, Yahya bin Harith told me, from Qasim Abu Abdul-Rahman, from Uqba bin Amir, who related it. Its isnad is hasan because of Qasim, who is Ibn Abdul-Rahman Dimashqi Abu Abdul-Rahman. Ibn Hibban criticized him, while the others graded him hasan, and he is hasan al-hadith.On this subject there is also a report from Abu Umama, from the Prophet ﷺ, who said, "Whoever fasts a day in the cause of Allah, Allah places between him and the Fire a trench as wide as the distance between heaven and earth." Narrated by Tirmidhi (1624) from Ziyad bin Ayub, who said, Yazid bin Harun told us, Walid bin Jameel told us, from Qasim Abu Abdul-Rahman, from Abu Umama, who related it. Tirmidhi said, "This is a hadith gharib from the hadith of Abu Umama." I say, it contains Walid bin Jameel, who is Filastini, weak in hadith. Abu Hatim said, "A shaykh who narrates unrecognized hadiths from Qasim."On this subject there is also what has been reported from Abu Darda, who said, the Messenger of Allah ﷺ said, "Whoever fasts a day in the cause of Allah, Allah distances the Fire from him by a journey of a thousand years for a swift rider." Narrated by Ahmad (27503) from Abu Saeed, who said, Abu Yaqub, meaning Ishaq bin Uthman Kullabi, told us, he said, I heard Khalid bin Durayk narrating from Abu Darda, who related it in a long hadith. Khalid bin Durayk is Shami, and it is not mentioned in his biography that he ever met Abu Darda. He also narrated from Ibn Umar and Ayesha without having met either of them, and Haythami also faulted it in Majma (5/285) for being disconnected.It has other isnads as well, one of which was narrated by Tabarani in Awsat (3598) through Abdullah bin Walid Adani, who said, Sufyan Thawri told us, from Amash, from Shamir bin Atiya, from Shahr bin Hawshab, from Umm Darda, from Abu Darda, who said, the Messenger of Allah ﷺ said, "Whoever fasts a day in the cause of Allah, Allah places between him and the Fire a trench as wide as the distance between heaven and earth." Tabarani said, "No one narrated this hadith from Sufyan except Abdullah bin Walid Adani." I say, Adani was among the companions of Sufyan Thawri. Ahmad said, "He heard from Sufyan, and his hearing was established, but he was not a man devoted to hadith, and his hadith is sahih hadith. He would sometimes err and make mistakes in the isnad. I myself wrote down a great deal from him." As for Ibn Main, he said, "I do not know him, I never wrote anything from him." The isnad also contains Shahr bin Hawshab, about whom there is well-known criticism. Despite all this, Munziri said in Targhib wal-Tarhib (1484), after attributing it to Tabarani in Awsat and Saghir, "Its isnad is hasan."On this subject there is also what has been reported from Amr bin Abasa, who said, I heard the Messenger of Allah ﷺ say, "Whoever fasts a day in the cause of Allah, Allah distances him from the Fire by seventy autumns." Narrated by Ibn Abu Asim in al-Jihad (170) from Muhammad bin Ali, Abdullah bin Sulaym told us, from Ubaydullah bin Amr, from Zayd bin Abu Unaysa, from Junada bin Abu Khalid, from Abu Shayba, from Amr bin Abasa, who related it. It contains Junada bin Abu Khalid, who is Abu Khattab Dimashqi. Bukhari gave him a biographical entry in Tarikh al-Kabir, and Ibn Abu Hatim did likewise in Jarh wal-Tadil, and both remained silent about him, placing him among the unknown narrators, except that Ibn Hibban mentioned him in Thiqat (6/150), following his usual practice of confirming the reliability of anyone against whom no criticism has been recorded. Dhahabi said in Mizan, "Not known." His shaykh, Abu Shayba, is Mahri. Dhahabi said in the biography of "Bilaj Mahri" (1/352), "From Abu Shayba Mahri, from Thawban, that he vomited and so broke his fast, it is not known who this is nor who his shaykh is." Bukhari said, "Its isnad is not well known." End of quote.Tabarani also narrated it in Awsat (3273) from Bakr bin Sahl, from Yahya bin Hamza, from Numan bin Munzir, from Makhul, who said, Amr bin Abasa said, the Messenger of Allah ﷺ said, "Whoever fasts a day in the cause of Allah, the Fire is distanced from him by a journey of a hundred years." But Makhul never heard directly from Amr bin Abasa. Abu Hatim said, "I asked Abu Mushir whether Makhul heard from any of the companions of the Prophet ﷺ, and he said, Nothing has been established for me as sound except from Anas bin Malik." There is also disagreement over whether he heard from Wathila bin Asqa, with Abu Zura denying that he heard from him. As for Amr bin Abasa, I have not found anyone who explicitly stated that Makhul heard from him. Munziri did not notice this issue, saying in Targhib wal-Tarhib (1458), after attributing it to Tabarani in Kabir and Awsat, "Its isnad is not problematic." But how could it not be problematic when it contains a break in transmission.On this subject there is also a report from Utba bin Abd Sulami, who said, the Messenger of Allah ﷺ said, "Whoever fasts a day in the cause of Allah as an obligatory fast, Allah distances him from Hell by a distance equal to that between the seven heavens and the seven earths. And whoever fasts a day as a voluntary fast, Allah distances him from Hell by a journey equal to the distance between heaven and earth." Narrated by Tabarani in Kabir (17/119–120) through Muhammad bin Umar Waqidi, Thawr bin Yazid told us, from Shurayh bin Ubayd, from Utba bin Abd Sulami, who related it. It contains Muhammad bin Umar Waqidi, who is matruk. Ibn Abu Asim also narrated it in al-Jihad (172) from Muhammad bin Yahya bin Abdul-Kareem, who said, a man told us, and he did name him for me, who said, Thawr bin Yazid told us with his isnad, similarly. It contains an unnamed man, and it would not be surprising if he were Waqidi himself, since Muhammad bin Yahya had indeed named him, but the copyists removed his name because of his severe weakness, thereby giving the false impression that he was someone else.On this subject there is also what has been reported from Muaz bin Anas, who said, the Messenger of Allah ﷺ said, "Whoever fasts a day in the cause of Allah voluntarily, outside of Ramadan, is distanced from the Fire by a hundred years' journey of a swift, noble racehorse." Narrated by Abu Yaala (1486) from Ahmad bin Isa, Ibn Wahb told us, Yahya bin Ayub told me, from Zabban bin Fayd, from Sahl bin Muaz, from his father, who related it. Zabban bin Fayd Misri, Abu Juwayn, is daif. He was declared daif by Ahmad, Ibn Main, Ibn Hibban, and others. Haythami faulted the hadith on this basis in Majma (3/194), while also noting that he had been deemed reliable by someone. His statement, "he had been deemed reliable," apparently refers to Ibn Hibban's mention of him, but Ibn Hibban did not mention him in Thiqat, rather he mentioned him in Majruhin (373) and said, "Extremely munkar in hadith, he alone transmits from Sahl bin Muaz a whole set of narrations that appear to be fabricated, he cannot be relied upon." He also cited Ibn Main's judgment of daif regarding him.