15:9
إِنَّا نَحْنُ نَزَّلْنَا ٱلذِّكْرَ وَإِنَّا لَهُۥ لَحَـٰفِظُونَ ٩
Saheeh International
Indeed, it is We who sent down the Qur'an and indeed, We will be its guardian.
Tafsir of "Ibn Kathir" (English)
Verily, We, it is We Who revealed the Dhikr (i.e. the Qur'an) and surely We will guard it (from corruption).Allah, may He be exalted, stated that He is the One Who revealed the Dhikr to him, which is the Qur'an, and He is protecting it from being changed or altered