According to search-discovered classical Islamic scholarship, the believer's conduct 'towards other Muslims' is governed by the foundational principle of Ukhuwwah (brotherhood). The tafsir of Quran 33:6 by authorities like Ibn Kathir and Al-Qurtubi provides a masterclass in this concept. While the verse legally establishes the precedence of blood relatives ('Ulul-Arham') in matters of inheritance, abrogating earlier pacts, it crucially includes the exception: "except that you may do to your close associates a kindness." Ibn Kathir clarifies these 'associates' are the fellow believers. This codifies the enduring spiritual and social obligation of support, love, and goodwill towards the entire Muslim Ummah, creating a divinely ordained balance between the rights of the family and the unity of the community. This synthesis establishes that while legal duties like inheritance are kinship-based, moral and spiritual duties of brotherhood are universal for all Muslims.