How does Allah forgive an unbeliever all his sins—including adultery, drinking alcohol, and murder—merely upon his utterance of the Two Testimonies at the time of his death, while a Muslim is held accountable for his misdeeds? And is this just?

We must not speak about the religion of Allah without knowledge, nor object to His rulings. Rather, we should submit to them and not deny what we have not encompassed with knowledge, for denying something one has not encompassed with knowledge is characteristic of the unjust.

There should be no objection to Allah's mercy, for no one enters Paradise by their deeds, but rather by Allah's mercy.

Allah's forgiveness for a disbeliever comes after their conversion to Islam, meaning their transformation into a repentant Muslim. As for the disobedient Muslim, they are forgiven through repentance. Allah pardons the past sins of both.

Allah's bounty is immense; He forgives sins, accepts repentance, and transforms evil deeds into good ones for those who repent. This applies to the disbeliever if they embrace Islam, and to the disobedient person if they repent. The matter is not so simple that a person can disbelieve or disobey and then repent whenever they wish, for the issue is tied to Allah's divine enabling grace.

The ultimate outcome is what matters. Allah accepts the repentance of the disobedient and the Islam of the disbeliever as long as they have not reached the throes of death. And the deeds of a Muslim are annulled if they end their life in apostasy.

Allah Almighty accepts the repentance of a servant as long as they have not reached the throes of death. This is from His immense bounty and mercy. Allah is just; He does not wrong even an atom's weight, and He is bountiful, multiplying good deeds.