The Prophet ﷺ said, "Whoever fasts one day in the path of Allah, Allah will distance him from the Fire by seventy autumns." One of them says "seventy" and the other says "forty."
حدثنا قتيبة حدثنا ابن لهيعة عن أبي الأسود عن عروة بن الزبير وسليمان بن يسار أنهما حدثاه
عن النبي ﷺ قال من صام يوما في سبيل الله زحزحه الله عن النار سبعين خريفا أحدهما يقول سبعين والآخر يقول أربعين
[Hasan] The hadith has supporting narrations in Nasai, 4/172, 173, no. 2246-2252 (Fasting, chapter on the reward of one who fasts a day in the path of Allah, Mighty and Sublime, etc.), and Muslim, no. 1153, among others.On this subject there are also narrations from Abu Saeed [coming up: 1623], Anas [I did not find it], Uqba bin Amir [Nasai, no. 2256], and Abu Umama [coming up: 1624].