Chapter on I'tikaf (spiritual Retreat)
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 2|Chapter 38
وَ فِي رِوَايَةِ اَلسَّكُونِيِّ بِإِسْنَادِهِ قَالَ قَالَ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ: «اِعْتِكَافُ عَشْرٍ فِي شَهْرِ رَمَضَانَ يَعْدِلُ حَجَّتَيْنِ وَ عُمْرَتَيْنِ».
In a narration from Al-Sakuni, with his chain of transmission, it is reported that the Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) said: "Performing i'tikaf for ten days in the Month of Ramadan is equivalent to two Hajj and two Umrah."
- Ṣaḥīḥ al-Faqīh