Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:28:52 –

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

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˺.
القرآن:٢٨:٥٢ –

الَّذِينَ آتَيْنَاهُمُ الْكِتَابَ مِنْ قَبْلِهِ هُمْ بِهِ يُؤْمِنُونَ  

{الذين آتيناهم الكتاب من قبله} أي القرآن {هم به يؤمنون} أيضا نزلت في جماعة أسلموا من اليهود كعبد الله بن سلام وغيره ومن النصارى قدموا من الحبشة ومن الشام.

See similar narrations below:

Collected by Qurʾān
quran:43:21 –

Or have We given them a book before the Qur'an to which they are adhering?  

Or have We brought them a scripture before, that is, ˹before˺ the Qur’ān, that they should worship other than God, so that they are holding fast to it? In other words, this never happened.
القرآن:٤٣:٢١ –

أَمْ آتَيْنَاهُمْ كِتَابًا مِنْ قَبْلِهِ فَهُمْ بِهِ مُسْتَمْسِكُونَ  

{أم آتيناهم كتاباً من قبله} أي القرآن بعبادة غير الله {فهم مستمسكون} أي لم يقع ذلك.