"wa taqatta'u amrahum baynahum" (and they tore their affairs apart among themselves) means: the People of the Scripture; that is, they divided their religion which they were commanded to follow, meaning: Islam, [and so they entered into] something else.
﴿وتقطعوا أَمرهم بَينهم﴾ يَعْنِي: أَهْلَ الْكِتَابِ؛ أَيْ: فَرَّقُوا دِينَهُمُ الَّذِي أُمِرُوا بِهِ، يَعْنِي: الْإِسْلَام [فَدَخَلُوا فِي] غَيره.