Surah Fussilat 41:3

كِتَـٰبٌ فُصِّلَتْ ءَايَـٰتُهُۥ قُرْءَانًا عَرَبِيًّا لِّقَوْمٍ يَعْلَمُونَ

A Book whose verses have been detailed, an Arabic Qur’ān for a people who know,

Translation: Saheeh International

Tafsir

A Book kitābun the predicate thereof whose signs have been set out in detail whose signs have been expounded through various rulings stories and admonitions as an Arabic Qur’ān qur’ānan ‘arabiyyan a circumstantial qualifier referring to kitābun ‘a Book’ by qualifying it adjectivally for a people li-qawmin is …

Excerpt from Tafsir al-Jalalayn, commentary on 41:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.