How is the Hadith understood: "It is the right of the servants upon Allah that He not punish anyone who does not associate partners with Him," and does it mean that a monotheist will not be punished no matter what sins they commit?

Ibn Hajar, in Fath al-Bari, discussed the meaning of the hadith "No one who says 'La ilaha illa Allah' (There is no god but Allah) will enter the Fire," clarifying that it seems to contradict the abundant texts from the Qur’an and Sunnah which state that some disobedient monotheists will enter the Fire. Scholars have adopted various approaches to reconcile these two aspects, among them:

The saying of Al-Zuhri that the concession (rukhsa) was valid before the revelation of the obligatory duties (fara'id) and legal punishments (hudud). This opinion was deemed unlikely because abrogation (naskh) does not apply to news reports (khabar), and due to Mu'adh's delayed hearing of the hadith.

Another view is that there is no abrogation, but rather the hadith is to be understood in its generality, qualified by conditions, as Wahb ibn Munabbih indicated by saying: "There is no key except that it has teeth."

Another interpretation is that it means not entering the Fire of shirk (polytheism).

Yet another view is that it means not punishing the entire body of monotheists, because the Fire does not burn the places of prostration.

Finally, it is said that it is specific to those who are sincere (mukhlis), and sincerity necessitates the heart’s realization of the meaning. This cannot be imagined alongside persistence in disobedience, because a heart filled with the love and fear of Allah will compel the limbs towards obedience and deter them from disobedience.