﴿ إِلَّا تَنفِرُوا۟ يُعَذِّبْكُمْ عَذَابًا أَلِيمًۭا وَيَسْتَبْدِلْ قَوْمًا غَيْرَكُمْ وَلَا تَضُرُّوهُ شَيْـًۭٔا ۗ وَٱللَّهُ عَلَىٰ كُلِّ شَىْءٍۢ قَدِيرٌ ﴾

“If you do not go forth to war [in God's cause], He will chastise you with grievous chastisement, and will place another people in your stead - whereas you shall in no wise harm Him: for, God has the power to will anything.”

If illā lā has been assimilated with the nūn of the conditional particle in in both instances here and in the next verse you do not go forth if you do not set out with the Prophet s for the struggle He will chastise you with a painful chastisement and He will substitute you with another folk other than you that is He will bring them in your place and you will not hurt Him that is God or ‘him’ as being the Prophet s at all should you neglect to help him to victory for God Himself will indeed bring victory to His religion; for God has power over all things including bringing victory to His religion and His Prophet.