Allah doth blot out or confirm what He pleaseth: with Him is the Mother of the Book.
Al-Rāzī explains that God effaces what He will and establishes means
that, in accordance with what the Divine Will has decreed, “He brings things into
existence at one moment and makes them nonexistent at another; gives life at
one moment and causes death at another; bestows riches at one moment and
causes poverty at another.” The Mother of the Book (Umm al-kitāb; cf. 3:7; 43:4)
refers, according to some, to the fundamental source of Divine Revelation from
which the Quran and other Divinely revealed books are transcribed (Ṭ); others
identify it with the Preserved Tablet mentioned in 85:22 (see 85:22c; Bg, Kl, R,
Z), and still others say it refers to God’s Knowledge (R).
Nasr, Hossein (2015). Study Quran. http://www.islamicweblibrary.com/wp-content/uploads/2020/04/TheStudyQuran.pdf