I'tikaaf is an individual act of worship, not a collective one. It is Sunnah ala al-Kifayah (سنة على الكفاية), meaning that if at least one person in a mosque observes I'tikaaf, the Sunnah is fulfilled on behalf of the entire neighbourhood. If it were a collective act of worship, there would have been an obligation on at least two individuals, as is the case with congregational prayer, which requires a minimum of two people.
The purpose of I'tikaaf is to disconnect from worldly distractions, to isolate and devote oneself entirely to Allah’s worship and remembrance, seeking inner peace and spiritual focus. This objective is best achieved through individual worship.
Abu Sa‘eed (may Allah be pleased with him) reported:
The Messenger of Allah (peace and blessings be upon him) observed I’tikaaf in the mosque. He heard some people reciting the Qur’an aloud, so he lifted the curtain and said:
"Behold! Each of you is engaged in intimate discourse with his Lord, so do not disturb one another and do not raise your voices over one another in recitation."
Or he said: "In prayer."
(Musnad Ahmad, Hadith No. 11986, Vol. 18, p. 392, Mu’assasat ul-Risalah)
This hadith indicates that I'tikaaf is an individual act of worship, as the Prophet (peace and blessings be upon him) engaged in it individually.
In summary, I'tikaaf is an individual act of worship. However, if a Shaykh or Imam, for the purpose of spiritual training, introduces a structured program that includes Qur’an recitation correction, prayer practice, religious lectures, and Islamic teachings, there is room for the permissibility of such an arrangement.
Nevertheless, taking part in the various group activities should not be made compulsory. Those who prefer to remain engaged in their individual acts of worship should not be forced to join, nor should they be considered sinful or condemned for not taking part.
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دلائل:
الدر المختار مع رد المحتار: (442/2، ط: دار الفکر)
وسنة مؤكدة في العشر الأخير من رمضان) أي سنة كفاية كما في البرهان وغيره لاقترانها بعدم الإنكار على من لم يفعله من الصحابة۔
(قوله أي سنة كفاية) نظيرها إقامة التراويح بالجماعة فإذا قام بها البعض سقط الطلب عن الباقين۔
حجۃ اللہ البالغۃ: (86/2، ط: دار الجیل)
ولما كان الاعتكاف في المسجد سببا لجمع الخاطر وصفاء القلب والتفرغ للطاعة والتشبه بالملائكة والتعرض لوجدان ليلة القدر اختاره النبي صلى الله عليه وسلم في العشر الأواخر وسنه للمحسنين من أمته، قالت عائشة رضي الله عنها: السنة على المعتكف ألا يعود مريضا، ولا يشهد جنازة ولا يمس المرأة، ولا يباشرها، ولا يخرج إلا لحاجة إلا ما لا بد منه۔
فتاوی قاسمیۃ: (547/11، ط: مکتبہ اشرفیۃ)
Allah the Almighty knows best.
Darul Ifta Al-Ikhlas, Karachi.