He, Exalted is He, also says:
“Allah has sent down the finest discourse: a Book, consistent and oft-repeated.” ⦗39:23⦘

And He says:
“We relate to you the best of stories by revealing this Quran to you.” ⦗12:3⦘

With these verses He makes it clear that He has revealed this Quran as a guardian over the scriptures that preceded it. A guardian (muhaimin) is a witness, a trustworthy custodian and a judge: it bears witness to the truth still found in those books, rejects whatever has been distorted in them, affirms the rulings Allah has maintained, and abrogates whatever Allah has abrogated. In all of this it is the source to be trusted.

He has also declared the Quran to be the finest discourse and the finest of narratives. This entails that anyone who held fast to the Torah before its rulings were abrogated—without altering any part of them—was among the people of faith and guidance; and likewise, anyone who adhered to the Gospel, with no change in its rulings before abrogation, was also among the people of faith and guidance. The passage offers no praise to someone who clings to a law that has been altered, let alone to one who clings to a law that has been abrogated and refuses to believe in the messengers Allah later sent and the books He revealed. On the contrary, the Quran repeatedly declares the unbelief of the Jews and the Christians for altering the first Scripture and for failing to believe in Muhammad—may Allah bless him and grant him peace.

As for their interpretation of His words, “That Book…” ⦗2:2⦘ as meaning the Gospel, and of His words, “those who believe in the unseen, establish the prayer, and spend out of what We have provided for them” ⦗2:3⦘