The Quran

إِنَّ الَّذينَ كَفَروا وَصَدّوا عَن سَبيلِ اللَّهِ وَشاقُّوا الرَّسولَ مِن بَعدِ ما تَبَيَّنَ لَهُمُ الهُدىٰ لَن يَضُرُّوا اللَّهَ شَيئًا وَسَيُحبِطُ أَعمالَهُم

Muhammad Asad

Verily, they who are bent on denying the truth and on barring [others] from the path of God, and [who thus] cut themselves off from the Apostle¹ after guidance has been vouchsafed to them, can in no wise harm God; but He will cause all their deeds to come to nought.

For the above rendering of shaqqu, see note 16 on 8:13. The "cutting oneself off" from the Apostle signifies, of course, a rejection of his message, and, in this particular context, a refusal to follow the Qur'anic call to fight in a just cause, i.e., in defence of the Faith or of freedom (see note 167 on 2:190).