Which is the best book or chapter that elaborates on the complements of repentance that make repentance complete, and is the chapter on repentance in Madarij al-Salikin the best? And what is the extent of validity in using the hadith about the last person to exit Hellfire as evidence for the changing of sins into good deeds for the repentant sinner in this world, and are they equivalent?

The answer referenced several sources concerning repentance, its virtues, and its conditions, including "Ihya' 'Ulum al-Din" by Al-Ghazali, "Madarij al-Salikin" by Ibn al-Qayyim, "Al-Adab al-Shar'iyyah" by Ibn Muflih, and "Mawsu'at al-Muslim fi al-Tawbah" (The Muslim Encyclopedia on Repentance) by Dr. Munir al-Bayyati.

It explained that sincere repentance (Tawbah Nasuh), when its conditions are met, causes Allah to transform evil deeds into good deeds. This transformation includes the disbeliever who embraces Islam and the disobedient Muslim who repents, citing Allah's saying: "Except for those who repent, believe and do righteous work. For them Allah will change their evil deeds into good ones" (Al-Furqan: 70). Authentic hadiths were mentioned confirming the transformation of evil deeds into good deeds for the disbeliever who embraces Islam, as in the hadith of Abu Farwah Shatab and the hadith of Abu Dharr in Sahih Muslim.

It affirmed that the transformation applies to one who regrets their evil deeds, and that all their sins become a cause for righteous deeds that erase them. It urged continuation in making up missed prayers and increasing supererogatory acts and acts of obedience; because the erasure of evil deeds through Islam and sincere repentance is more beloved to Allah than their erasure through punishment. There is no contradiction between the verse and the hadith; the hadith is presented in the context of Allah's increased grace and generosity.