We responded to the claims of two unbelievers that "the Quran has been altered" with 6 proofs. Finally, one of them repeat the Shahadah.

“It is better than everything over which the sun rises and sets for you when Allah guides a person to the straight path through you.”
(Jamius-Saghir, 3/192; Majmauz-Zawaid, h. no: 9787)