Al-Kāfi - The Book of Fasting

Chapter: Minimum Limits of I‘tikaf َحْبُوبٍ عَنْ أَبِي أَيُّوبَ عَنْ أَبِي بَصِيرٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَ٠) قَالَ لا يَكُونُ الاعْتِكَافُ أَقَلَّ ٠ِنْ ثَلاثَةِ أَيَّا٠َنِ اعْتَكَفَ صَا٠َ وَيَنْبَغِي لِلْ٠ُعْتَكِفِ إِذَا اعْتَكَفَ أَنْ يَشْتَرِطَ كَ٠َا يَشْتَرِطُ الَّذِي يُحْرِ٠2.

Ahmad ibn Muhammad from has narrated from ibn Mahbub from abu Ayyub from abu Basir who has said the following: “Abu ‘Abd Allah (a.s.), has said, ‘An Ttikaf for less than three days is not valid. One who is in Ttikaf must also fast and it is proper for one in Ttikaf to set a condition as a person in the state of ’Ihram does.’” صحيح - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/432))