صيام التطوع
Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "If anyone fasts a day for the sake of Allah, Allah shall keep his face away from Hell (the distance of) seventy years."
عن أبي سعيد الخُدْرِي -رضي الله عنه- قال: قال رسول الله -صلى الله عليه وسلم-: «من صام يومًا في سبيل الله بَعَّدَ الله وجهه عن النَّار سَبْعِين خريفا».
شرح الحديث :
The Prophet (may Allah's peace and blessings be upon him) informs us in this Hadīth that anyone who fasts one day while performing Jihad, Allah shall reward him by distancing his face away from Hell for seventy years. That is because fasting in this case combines the hardship of Jihad and that of remaining steadfast, in addition to the hardship of fasting. Distancing him away from Hell requires moving him closer to Paradise, for there are only two paths: one to Paradise and the other to Hellfire.