Surah At-Tawbah 9:36

إِنَّ عِدَّةَ ٱلشُّهُورِ عِندَ ٱللَّهِ ٱثْنَا عَشَرَ شَهْرًا فِى كِتَـٰبِ ٱللَّهِ يَوْمَ خَلَقَ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضَ مِنْهَآ أَرْبَعَةٌ حُرُمٌ ۚ ذَٰلِكَ ٱلدِّينُ ٱلْقَيِّمُ ۚ فَلَا تَظْلِمُوا۟ فِيهِنَّ أَنفُسَكُمْ ۚ وَقَـٰتِلُوا۟ ٱلْمُشْرِكِينَ كَآفَّةً كَمَا يُقَـٰتِلُونَكُمْ كَآفَّةً ۚ وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ مَعَ ٱلْمُتَّقِينَ

Indeed, the number of months with Allāh is twelve [lunar] months in the register of Allāh [from] the day He created the heavens and the earth; of these, four are sacred. That is the correct religion [i.e., way], so do not wrong yourselves during them. And fight against the disbelievers collectively as they fight against you collectively. And know that Allāh is with the righteous [who fear Him].

Translation: Saheeh International

Tafsir

Verily the number of months used to reckon the year with God is twelve months in the Book of God the Preserved Tablet al-lawh al-mahfūz from the day that He created the heavens and the earth; four of them that is the months are sacred inviolable Dhū’l-Qa‘da Dhū’l-Hijja Muharram and Rajab. …

Excerpt from Tafsir al-Jalalayn, commentary on 9:36, via Quran.com. The reader has the full commentary and 9 more tafsirs.