The I'tikaf in the last ten days of Ramadan.

وَالاِعْتِكَافِ فِي الْمَسَاجِدِ كُلِّهَا، لِقَوْلِهِ تَعَالَى: {وَلاَ تُبَاشِرُوهُنَّ وَأَنْتُمْ عَاكِفُونَ فِي الْمَسَاجِدِ تِلْكَ حُدُودُ اللَّهِ فَلاَ تَقْرَبُوهَا كَذَلِكَ يُبَيِّنُ اللَّهُ آيَاتِهِ لِلنَّاسِ لَعَلَّهُمْ يَتَّقُونَAnd I‘tikaf may be practised in any mosque, as is evident in the Statement of Allah تعالى: “... And do not have sexual relations with them (your wives); while you are in I‘tikaf [i.e., confining oneself in a mosque for Salat (prayers) and invocations leaving the worldly activities for a limited number of days] in the mosques. These are the limits (set) by Allah; so approach them not. Thus does Allah make clear His Ayat (proofs, evidences, verses, lessons, signs, revelations, laws, legal and illegal things, Allah’s set limits, orders), to mankind that they may become Al-Muttaqun (the pious).” (V.2:187)