إِلَّا تَنفِرُواْ يُعَذِّبۡكُمۡ عَذَابًا أَلِيمٗا وَيَسۡتَبۡدِلۡ قَوۡمًا غَيۡرَكُمۡ وَلَا تَضُرُّوهُ شَيۡـٔٗاۗ وَٱللَّهُ عَلَىٰ كُلِّ شَيۡءٖ قَدِيرٌ ٣٩
If you do not go forth, He will punish you with a painful punishment and will replace you with another people, and you will not harm Him at all. And Allāh is over all things competent.
Translation: Saheeh International (English)
Each word's meaning and sound
If you do not go forward, striving for the sake of Allah to fight against the enemy, Allah will repay you with defeat and humiliation, and He will replace you with another people who are devoted to Allah, who rush to fight when they are called to do so. You do not harm Him in any way by going against His command, because He has no need of you, while you are in need of Him. Allah has power over all things, nothing weakens Him, and it is easy for Him to make His path and His Prophet triumph without you.
Al-Mukhtasar in interpreting the Noble Quran