{ As We have sent down to those who make divisions, those make pieces out of the Qur’an } Al-hijr 90-91

Regarding His word { As We have sent down to those who make divisions, those make pieces out of the Qur’an } , Ibn 'Abbas said: These are the People of the Book, who divided it into pieces and made it into individual parts, then believed in some of it and disbelieved in some of it.
Tafsir Al-Tabari

{ Pieces } [‘iDeen] : parts of a whole, the plural of ‘iDah, derived from ‘uDwah, an act of ‘aDDa to a sheep, when it is dismembered.
Tafsir Al-Zamakhshari

{ Those who make pieces out of the Qur’an } : they divided it into pieces and made it into individual parts, then believed in some of it and disbelieved in some of it. Mujahid said: These are the Jews and the Christian, who divided up their book, separated parts of it, and altered it. … { Pieces } : it is said that this is the plural of part/member [‘uDw], taken from their way of speaking “I broke something into parts”, i.e. “I separated it”.