How do scholars differ in determining the abrogating and abrogated verses, even though the Prophet, peace and blessings be upon him, clarified that, and Allah says: "This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion"?

Abrogation (Naskh), linguistically, means transformation, transfer, removal, and obliteration. Technically, it means the removal of a legal ruling by a later discourse. Abrogation in the Qur’an occurs in several forms, including: the abrogation of the recitation while the ruling remains, and the abrogation of both the recitation and the ruling. Abrogation applies only to rulings, not to narratives, and this is the view of the majority of scholars. Its existence is substantiated by the verse: ﴿Whatever verse We abrogate or cause to be forgotten, We bring forth [one] better than it or similar to it.﴾ [Al-Baqarah: 106].

The benefits of abrogation include: demonstrating the obedience of the servants, easing burdens upon them, and gradualism in legislation. Abrogation may be from a more difficult ruling to a lighter one, or vice versa, or from a similar ruling to a similar one, or without a substitute. Abrogation occurs between the Qur’an and the Sunnah, and it is permissible to abrogate the Qur’an by the Sunnah and vice versa.

Abrogation is specific to the time of the Prophet ﷺ, and there is no abrogation after his death and the establishment of the Shari'ah. Consensus (Ijma’) is neither abrogated nor does it abrogate. The disagreement among scholars regarding issues of abrogation is due to the non-receipt of abrogating texts, or differences in the authenticity of abrogating reports and the methods of abrogation.