Chapter on I'tikaf (spiritual Retreat)
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 38
وَ رُوِيَ عَنْ دَاوُدَ بْنِ سِرْحَانَ قَالَ: كُنْتُ بِالْمَدِينَةِ فِي شَهْرِ رَمَضَانَ فَقُلْتُ لِأَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ إِنِّي أُرِيدُ أَنْ أَعْتَكِفَ فَمَا ذَا أَقُولُ وَ مَا ذَا أَفْرِضُ عَلَى نَفْسِي فَقَالَ «لاَ تَخْرُجْ مِنَ اَلْمَسْجِدِ إِلاَّ لِحَاجَةٍ لاَ بُدَّ مِنْهَا وَ لاَ تَقْعُدْ تَحْتَ ظِلاَلٍ حَتَّى تَعُودَ إِلَى مَجْلِسِكَ.
It is narrated from Dawud ibn Sirhan, who said: "I was in Medina during the Month of Ramadan, and I said to Abu Abdullah عليه السلام: 'I wish to perform i'tikaf. What should I say, and what should I make obligatory upon myself?' Imam عليه السلام said: 'Do not leave the mosque except for an unavoidable necessity, and do not sit under any shade until you return to your place in the mosque.'"
- Ṣaḥīḥ al-Faqīh