Surah At-Tawbah, verse 37

إِنَّمَا ٱلنَّسِىٓءُ زِيَادَةٌ فِى ٱلْكُفْرِ ۖ يُضَلُّ بِهِ ٱلَّذِينَ كَفَرُوا۟ يُحِلُّونَهُۥ عَامًا وَيُحَرِّمُونَهُۥ عَامًا لِّيُوَاطِـُٔوا۟ عِدَّةَ مَا حَرَّمَ ٱللَّهُ فَيُحِلُّوا۟ مَا حَرَّمَ ٱللَّهُ ۚ زُيِّنَ لَهُمْ سُوٓءُ أَعْمَـٰلِهِمْ ۗ وَٱللَّهُ لَا يَهْدِى ٱلْقَوْمَ ٱلْكَـٰفِرِينَ ﴿٣٧﴾

9:37 The postponement of [Sacred Months] is an act of disbelief, which leads them further astray. They declare a month lawful in one year and sacred the next year, in order to match the number of months that Allah has declared as sacred, thus making lawful what Allah has made forbidden; their evil deeds have been made appealing to them, and Allah does not guide the disbelieving people