"That is because they opposed Allah and His Messenger," meaning: they were enemies to Allah and His Messenger.
Tafsir of Surat al-Hashr from verse 5 to verse 6.
﴿ذَلِكَ بِأَنَّهُمْ شَاقُّوا اللَّهَ وَرَسُولَهُ﴾ عَادوا الله وَرَسُوله.
تَفْسِير سُورَة الْحَشْر من الْآيَة ٥ إِلَى آيَة ٦.
