he should cast evil into your hearts,” or he said, “something.” Agreed upon.

Explanation
These two reports are cited by the author—may Allah have mercy on him—in Riyāḍ al-Ṣāliḥīn.
The first is the ḥadīth of the Mother of the Believers, Ṣafiyyah bint Ḥuyayy (may Allah be pleased with her). The Prophet ﷺ was observing iʿtikāf (retreat in the mosque) during Ramaḍān, for iʿtikāf is only to be practiced in Ramaḍān. The Prophet ﷺ never performed it outside Ramaḍān except once: he had missed the last ten days in one Ramaḍān and therefore made them up in Shawwāl. Other than that, he did not legislate iʿtikāf for his community at any time outside Ramaḍān.

Iʿtikāf was instituted for the purpose of seeking Laylat al-Qadr. Initially, the Prophet ﷺ observed it during the first ten nights of Ramaḍān in hope of that night, then during the middle ten, until he was informed that it falls in the last ten nights; from then on he consistently performed iʿtikāf in the final ten.

As for the report in which ʿUmar asked the Prophet ﷺ about a vow—namely, that ʿUmar had vowed to observe iʿtikāf for one or two nights in the Sacred Mosque—and the Prophet ﷺ told him, “Fulfil your vow,” this does not establish iʿtikāf as a generally prescribed practice. It merely shows that fulfilling a vow by means of iʿtikāf is permissible and not sinful.

The Sunnah, therefore, is that iʿtikāf be limited to Ramaḍān, specifically to its last ten days, as the Prophet ﷺ did. Iʿtikāf means remaining in the mosque for the obedience of Allah so that a person may devote himself wholly to worship, and for no other purpose.