Can the قرين (Qareen) become Muslim, given that it is a jinn and possesses will and is subject to accountability?

The jinn are accountable and addressed by the message of the messengers; some of them are believers and some are disbelievers. Iblis is one of the jinn, and he is the chief of the devils. He has been condemned to eternal hellfire, with no possibility of repentance. As for the offspring and soldiers of Iblis, their inherent nature is rebellion and corruption.

There is a disagreement regarding the possibility of the Prophet's qarin (companion jinn) embracing Islam. Two different interpretations have been narrated for the word "fa'aslama" (فأسلم - meaning 'so he submitted' or 'so he became Muslim'): either the Prophet's devil became Muslim, or the Prophet was saved from its evil. The more probable opinion is that the Prophet was saved from the evil of his devil, because devils do not become Muslim.

Even if the Prophet's qarin embraced Islam, this is a unique characteristic of the Prophet and does not mean that other devils can become Muslim. A Muslim must beware of Satan and seek refuge from him. One should not delve into unseen matters about which they have no knowledge.