Shaykh Ibn Uthaymeen (rahimahullaah) said:

Regarding the Books of the People of the Book

In summary: That what has come in their books - meaning the previous [revealed] books - divides into two types and two things:

Firstly: That about which Allaah has narrated to us in the Qur'an, or the Messenger of Allaah (sallallaahu alayhi wasallam) [has narrated to us], then this is accepted, correct.

And secondly: What they [the people of the book] have narrated, then this does not escape from three situations:

• The first situation: That our legislation testifies to its falsity, it is obligatory upon us to hold it as false and to reject it.

• The second situation: That whose truthfulness our legislation testifies to, so we accept it as true and accept it due to the witness of our legislation over it.

• The third situation: What is neither from this (the first) or that (the second), it is obligatory upon us to withhold, because they do not believe, and [thus] in their report (khabar) there will occur lying, change, addition and decrease.

Source: Sharh Riyaadh as-Saaliheen 1/450, through "Mu'jam at-Ta'reefaat wad-Dawaabit wat-Taqseemaat wal-Fawaa'id Fil-Musannafaat al-I'itqaadiyyah Lish-Shaykh Ibn al-Uthaymeen", pp. 362-363.