And He says:
“We send down of the Quran that which is healing and mercy for the believers, but it increases the wrongdoers only in loss.” [Surah al-Isrā’ 82]
It is well known that repentance encompasses the return from evil deeds to good deeds. Hence, nothing erases all evil deeds except repentance. Apostasy encompasses the return from good deeds to evil deeds. Hence, nothing nullifies all good deeds except apostasy from faith.
Likewise, what we have mentioned concerning the varying degrees of evil deeds applies to disbelief, wickedness, and disobedience: some disbelievers are less evil than others. Thus, in their chapters on apostasy and embracing Islam, the jurists discuss a person’s passage from one religion to another—as when one spouse changes religion—as a passage to a religion better than, worse than, or equivalent to the former religion. They say that when a person belonging to the People of the Book becomes a Magian or a polytheist, he has moved to something worse than his former religion. When a polytheist or a Magian joins the People of the Book, he has moved to something better than his former religion. When a Christian becomes a Jew, or vice versa, he has moved to a religion equivalent to his own. By consensus, adherents of Magianism are allowed to remain in their religion. As for polytheism, according to some scholars, only certain people are allowed to remain in it. The Sabeans fall into two categories according to scholars who have carefully investigated the matter, while other scholars hold two differing views concerning them. Knowledge of the relative ranks of religions is needed in many contexts to understand the relative ranks of good deeds.
The jurists discuss this in order to determine the rulings concerning these people, their intermarriages, their slaughtered animals, the protection of their lives, fighting them, and allowing them to remain in their religion upon payment of the jizyah imposed on them, along with other rulings brought by the Book and the Sunnah concerning religious communities and factions