Can persistence in sin lead to the apostasy of turning away or to the permissibility of sin?

Ibn al-Qayyim defined the disbelief of aversion (kufr al-i’rad) as the heart's and hearing's turning away from the Messenger, so one neither believes him nor disbelieves him, neither befriends him nor antagonizes him, and does not listen to what he brought. As for Sheikh Muhammad ibn Abd al-Wahhab, he made it the tenth of the nullifiers of Islam, which is turning away from the religion of Allah Almighty, so one neither learns it nor acts upon it. What Ibn al-Qayyim mentioned is specific to the disbeliever whom aversion prevents from entering Islam, whereas what Sheikh Muhammad mentioned is general and includes what occurs from the disbeliever and what occurs from the Muslim, thereby causing him to apostatize.

Persistence in sin is not disbelief and has no relation to the nullifier of aversion. Ahl al-Sunnah wa al-Jama’ah (the People of the Sunnah and the Community) consider the one who persists in sin to be a transgressor (fasiq), not a disbeliever. A Muslim does not disbelieve due to a sin—other than polytheism—unless he deems it lawful (istihlal). Deeming something lawful is of two types: apparent, by explicitly stating that what is forbidden is lawful, thereby disbelieving both outwardly and inwardly. And inward, by believing in the lawfulness of something among the prohibited matters that are agreed upon without explicitly stating it, thereby disbelieving between him and Allah, while outwardly maintaining the ruling of Islam.

Persistence does not indicate deeming something lawful, as many sinners are overcome by desire and continue in sin while believing in its prohibition and their hearts disliking it. The danger for the one who persists in sin is a bad ending, or that his heart may become saturated with the sin and deem it lawful, for sins are the precursors to disbelief. Sheikh al-Islam Ibn Taymiyyah mentioned that a person does not commit forbidden acts except due to weak faith and love. If one does not dislike forbidden things, does not fear Allah in them, and does not hope for His mercy, then he is not a believer, but rather a disbeliever or a hypocrite.

In summary: Persistence in sin is a major sin, but it does not become disbelief except by deeming it lawful, and persistence is not evidence of deeming it lawful, but it may lead to it.