ذٰلِكَ بِأَنَّهُم شاقُّوا اللَّهَ وَرَسولَهُ ۖ وَمَن يُشاقِّ اللَّهَ فَإِنَّ اللَّهَ شَديدُ العِقابِ

That is because they opposed God and His Messenger. Whoever opposes God—God is severe in penalty.