Chapter on I'tikaf (spiritual Retreat)
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 38
وَ قَالَ أَبُو عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ: «كَانَتْ بَدْرٌ فِي شَهْرِ رَمَضَانَ فَلَمْ يَعْتَكِفْ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ فَلَمَّا أَنْ كَانَ مِنْ قَابِلٍ اِعْتَكَفَ عَشْرَيْنِ عَشْراً لِعَامِهِ وَ عَشْراً قَضَاءً لِمَا فَاتَهُ ».
Abu Abdullah عليه السلام said: "The Battle of Badr occurred in the Month of Ramadan, so the Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) did not perform i'tikaf that year. However, in the following year, he performed i'tikaf for twenty days: ten days for that year's obligation and ten days as compensation for what he had missed."
- Ṣaḥīḥ al-Faqīh