Is it permissible to perform i'tikaf (spiritual retreat in the mosque) in other than the three mosques?

The questioner : Is there a report from the Prophet (peace and blessings be upon him) that he permitted i'tikaf (spiritual retreat in the mosque) in other than al-Masjid al-Haram and al-Masjid al-Nabawi?

The Shaykh : The noble verse is general: . Our companion. Be patient, may Allah bless you. And the mosques are general. And the "al" in it is for generality, not for the definite article.
As for what is narrated from Hudhayfah (may Allah be pleased with him) that there is no i'tikaf (spiritual retreat in the mosque) except in the three mosques, this hadith, first, Ibn Mas'ud criticized the narration of Hudhayfah. He said, "Perhaps they mentioned it and I forgot," or a word to that effect.
And second, even if it is authentic, the meaning is that there is no complete i'tikaf (spiritual retreat in the mosque). This is supported by the fact that Muslims have continued to perform i'tikaf (spiritual retreat in the mosque) in mosques other than the three mosques. Then how can the address be general with this generality and then be restricted to three mosques that only one in a million of Muslims attends, while all Muslims are in other than the three mosques? It is far-fetched to apply the address of the Shari'ah to rare issues and leave the numerous issues. This is something a student of knowledge should note when using evidence. The parallel to this is that some people applied the saying of the Prophet (peace and blessings be upon him) to the one who dies with a vow of fasting upon him. It is said, how is this? The fasting of a vow, which does not occur except from one person after another, is applied to the hadith, while the obligatory fasting of Ramadan, which occurs from everyone who is eligible for the obligation, is discarded from the indication of the hadith. This is far-fetched.