Regarding the verse "Those who have made the Quran into portions" [Hijr 15:91], he said, "They are the People of the Book. They divided it into parts, believing in some of it and disbelieving in other parts."
{الذين جعلوا القرآن عضين} قال: هم أهل الكتاب، جزؤوه أجزاء، فآمنوا ببعضه، وكفروا ببعضه.
Bukhari narrated it in the Tafsir (4705) from Yaqub bin Ibrahim, who said, Hushaym narrated to us, Abu Bishr informed us, from Saeed bin Jubayr, from Ibn Abbas, and he related it.Some scholars of knowledge said, what is meant by "Quran" here is the scripture that was read among them, from the Torah and the Injil, so they believed in part of the scripture and disbelieved in part of it, such as the glad tidings of the Prophet ﷺ. The statement of Ibn Abbas can accommodate both meanings, and Mujahid held to the second meaning.