Chapter on I'tikaf (spiritual Retreat)
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 38
وَ رَوَى دَاوُدُ بْنُ اَلْحُصَيْنِ عَنْ أَبِي اَلْعَبَّاسِ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: «اِعْتَكَفَ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ فِي شَهْرِ رَمَضَانَ فِي اَلْعَشْرِ اَلْأُولَى ثُمَّ اِعْتَكَفَ فِي اَلثَّانِيَةِ فِي اَلْعَشْرِ اَلْوُسْطَى ثُمَّ اِعْتَكَفَ فِي اَلثَّالِثَةِ فِي اَلْعَشْرِ اَلْأَوَاخِرِ ثُمَّ لَمْ يَزَلْ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ يَعْتَكِفُ فِي اَلْعَشْرِ اَلْأَوَاخِرِ.
It is narrated by Dawud ibn Al-Husayn, from Abu Al-Abbas, from Abu Abdullah عليه السلام, who said: "The Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) performed i'tikaf in the first ten days of Month of Ramadan, then in the second ten days (the middle ten), and then in the last ten days. After that, the Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) consistently performed i'tikaf in the last ten days of Month of Ramadan."
- Ṣaḥīḥ al-Faqīh, p. 113