The "register" (كِتَٰبٍۢ مُّبِينٍۢ) referred to in Surah Hud, Ayah 6, is a divine, comprehensive record.

Tafsir Ibn Kathir states that Allah informs us that the provisions, dwelling places (مُسْتَقَرَّهَا), and ultimate resting places (مُسْتَوْدَعَهَا), or where creatures will die, are all "written in a Book with Allah that explains it in detail." This highlights its meticulous nature and divine origin.

This concept is supported by cross-references in the Quran. For instance, Surah 6:38 mentions, "We have neglected nothing in the Book," and Surah 6:59 states, "There is not a grain in the darkness of the earth nor anything fresh or dry, but is written in a Clear Record (كِتَٰبٍۢ مُّبِينٍۢ)." These verses emphasize the comprehensiveness of this divine register, encompassing all aspects of creation, known and unknown. The term "كِتَٰبٍۢ مُّبِينٍۢ" (clear register/book) signifies a record that is explicit, manifest, and leaves no doubt regarding its contents, encompassing all knowledge and predestination.

📚 Sources: Classical tafsir (multi-source)