﴿ وَإِنَّهُۥ لَهُدًۭى وَرَحْمَةٌۭ لِّلْمُؤْمِنِينَ ﴾

“and, verily, it is a guidance and a grace unto all who believe [in it].”

(And lo! It) i.e. the Qur'an (is a guidance) from error (and a mercy) shielding from the torment (for believers) in Muhammad (pbuh) and in the Qur'an.