Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
bayhaqi:8585Abū ʿAbdullāh al-Ḥāfiẓ And ʾAbū Saʿīd b. Abū ʿAmr > Abū al-ʿAbbās Muḥammad b. Yaʿqūb > Asīd b. ʿĀṣim > al-Ḥusayn b. Ḥafṣ > Sufyān > Ibn Jurayj > ʿAṭāʾ > Ibn ʿAbbās And Ibn ʿUmar Annahumā

[Machine] From Ibn Abbas and Ibn Umar, they said: "The one who is in Iʿtikāf should fast."  

البيهقي:٨٥٨٥أَخْبَرَنَا أَبُو عَبْدِ اللهِ الْحَافِظُ وَأَبُو سَعِيدِ بْنُ أَبِي عَمْرٍو قَالَا ثنا أَبُو الْعَبَّاسِ مُحَمَّدُ بْنُ يَعْقُوبَ ثنا أَسِيدُ بْنُ عَاصِمٍ ثنا الْحُسَيْنُ بْنُ حَفْصٍ عَنْ سُفْيَانَ عَنِ ابْنِ جُرَيْجٍ عَنْ عَطَاءٍ

عَنِ ابْنِ عَبَّاسٍ وَابْنِ عُمَرَ أَنَّهُمَا قَالَا الْمُعْتَكِفُ يَصُومُ