This book you are reading only uses some of the extracts from the Gospel that are compatible with the Qur'an and the Sunna of our Prophet Muhammad (may God bless him and grant him peace).

As revealed in the Qur'an, the Gospel, Torah, Psalms and the pages of Abraham are books sent down to prophets who lived in the past. Some of these books have disappeared, while others have been altered or distorted. But they nevertheless contain a great many correct pronouncements belonging to the true faith. Muslims analyze these according to the Qur'an and the Sunna [teachings of the Prophet Muhammad (may God bless him and grant him peace)] and decide that they are correct statements compatible with verses and the hadith. Therefore, statements in the Torah and the Gospel that conform to the Qur'an and the Sunna are statements that Muslims can benefit from. But the essential precondition is for these statements to be in agreement with the verses of the Qur'an and the hadiths.