Surah Al-Qasas 28:52

ٱلَّذِينَ ءَاتَيْنَـٰهُمُ ٱلْكِتَـٰبَ مِن قَبْلِهِۦ هُم بِهِۦ يُؤْمِنُونَ

Those to whom We gave the Scripture before it - they are believers in it.

Translation: Saheeh International

Tafsir

Those to whom We gave the Scripture before this that is before the Qur’ān they believe in it too. This was revealed regarding certain Jews who became Muslims such as ‘Abd Allāh b. Salām and others and certain Christians who had come from Abyssinia and Syria who also became Muslims.

Excerpt from Tafsir al-Jalalayn, commentary on 28:52, via Quran.com. The reader has the full commentary and 9 more tafsirs.