Surah Al-Hijr 15:1

الٓر ۚ تِلْكَ ءَايَـٰتُ ٱلْكِتَـٰبِ وَقُرْءَانٍ مُّبِينٍ

Alif, Lām, Rā. These are the verses of the Book and a clear Qur’ān [i.e., recitation].

Translation: Saheeh International

Tafsir

Alif lām rā’ God knows best what He means by these letters. Those — these verses — are the verses of the Book the Qur’ān āyātu’l-kitābi this annexation functions in the sense of min ‘from’ and of a manifest Qur’ān one that makes evident what is truth and what is falsehood wa-qur’ānin mubīnin is made up of a supplement …

Excerpt from Tafsir al-Jalalayn, commentary on 15:1, via Quran.com. The reader has the full commentary and 9 more tafsirs.