إِنَّمَا النَّسِيءُ زِيَادَةٌ فِي الْكُفْرِ يُضَلُّ بِهِ الَّذِينَ كَفَرُوا يُحِلُّونَهُ عَامًا وَيُحَرِّمُونَهُ عَامًا لِّيُوَاطِئُوا عِدَّةَ مَا حَرَّمَ اللَّهُ فَيُحِلُّوا مَا حَرَّمَ اللَّهُ زُيِّنَ لَهُمْ سُوءُ أَعْمَالِهِمْ وَاللَّهُ لَا يَهْدِي الْقَوْمَ الْكَافِرِينَ
Indeed nasee is an increase in unfaith, whereby the faithless are led [further] astray. They allow it in one year and forbid it another year, so as to fit in with the number, which Allah has made inviolable, thus permitting what Allah has forbidden. Their evil deeds appear to them as decorous, and Allah does not guide the faithless lot.
Agha Ali Puya Commentary
Commentary on Quran 9:37
[Pooya/Ali Commentary 9:37] Aqa Mahdi Puya says: The pagans of Arabia used to observe a year of 13 months after two years to combine the solar and lunar years, due to which they had to transfer the observance of Muharram to the succeeding month, Safar. This verse condemns their interference with that which Allah has ordained.