As for scholarly consensus, more than one scholar has reported it.

It is recommended at all times. This is what the author and others have stated. Thus, if you wished now—while we are in the month of Jumada—to observe i'tikaf tomorrow, or tonight and tomorrow, that would be recommended, provided it does not distract from something more important. If it does distract from something more important, then what is more important deserves greater consideration.

This issue, however, warrants further examination. For we say that Islamic rulings are received from the actions of the Messenger of Allah ﷺ, and the Messenger ﷺ did not observe i'tikaf outside Ramadan except to make it up. Likewise, as far as we know, none of his Companions observed i'tikaf outside Ramadan except to make it up. Nor has any general or unrestricted wording been reported from him, to our knowledge, establishing the legitimacy of i'tikaf at all times. Had it been legislated at all times, it would have been widely known and extensively transmitted, due to the strong motive for practising it and the widespread need to transmit it.

The most that has been reported is that Umar ibn al-Khattab asked the Prophet ﷺ for a legal ruling, saying that he had vowed to observe i'tikaf for a night, or for a day and a night, in al-Masjid al-Haram. He replied: “Fulfil your vow.” (1) Yet he did not prescribe this for his Ummah as a general legislation, such that people would be told: Observe i'tikaf in the mosques during Ramadan and outside Ramadan, for this is a sunnah.

What appears correct to me is that if a person observes i'tikaf outside Ramadan, he should not be censured, based on the fact that the Messenger ﷺ permitted Umar ibn al-Khattab to fulfil his vow. Had such a vow been disliked or prohibited, he would not have permitted him to fulfil it,