Those who have made their Scripture into parts are the people of the Scripture who divided it into portions and believed in a part of it and disbelieved the other.
Sahih al-Bukhari Book 65, Hadith 227
← Previous Hadith Allah's Messenger (ﷺ) said, "The Um (substance) of the Quran is the seven oft-repeated verses (Al- Mathaini) and is the Great Quran (i.e. Surat-al-Fatiha).

Sahih al-Bukhari Book 65, Hadith 226 Next Hadith → "As We have sent down (the Scripture) on those who are divided (Jews and Christians)." (15.90) They believed in part of it and disbelieved in the other, (and they) are the Jews and the Christians.

Sahih al-Bukhari Book 65, Hadith 228