What is the meaning of "mahil musaddiq" mentioned in the Hadith "Hold fast to the Qur'an, for it is a mahil musaddiq"?

The Qur'an will intercede for the one who follows it and acts upon it, and its intercession will be accepted for him, leading to the forgiveness of his errors. It will also be a truthful accuser against the one who abandons it and turns away from it, becoming a witness against him and a cause of his ruin.