48:15
سَيَقُولُ ٱلْمُخَلَّفُونَ إِذَا ٱنطَلَقْتُمْ إِلَىٰ مَغَانِمَ لِتَأْخُذُوهَا ذَرُونَا نَتَّبِعْكُمْ ۖ يُرِيدُونَ أَن يُبَدِّلُوا۟ كَلَـٰمَ ٱللَّهِ ۚ قُل لَّن تَتَّبِعُونَا كَذَٰلِكُمْ قَالَ ٱللَّهُ مِن قَبْلُ ۖ فَسَيَقُولُونَ بَلْ تَحْسُدُونَنَا ۚ بَلْ كَانُوا۟ لَا يَفْقَهُونَ إِلَّا قَلِيلًا
Those who remained behind will say when you set out toward the war booty to take it, "Let us follow you." They wish to change the words of Allah. Say, "Never will you follow us. Thus did Allah say before." So they will say, "Rather, you envy us." But [in fact] they were not understanding except a little.
Context in Surah Al-Fath
Nearby ayahs help place verse 48:15 in sequence and meaning.
وَمَن لَّمْ يُؤْمِنۢ بِٱللَّهِ وَرَسُولِهِۦ فَإِنَّآ أَعْتَدْنَا لِلْكَـٰفِرِينَ سَعِيرًا
And whoever has not believed in Allah and His Messenger - then indeed, We have prepared for the disbelievers a Blaze.
وَلِلَّهِ مُلْكُ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضِ ۚ يَغْفِرُ لِمَن يَشَآءُ وَيُعَذِّبُ مَن يَشَآءُ ۚ وَكَانَ ٱللَّهُ غَفُورًا رَّحِيمًا
And to Allah belongs the dominion of the heavens and the earth. He forgives whom He wills and punishes whom He wills. And ever is Allah Forgiving and Merciful.
قُل لِّلْمُخَلَّفِينَ مِنَ ٱلْأَعْرَابِ سَتُدْعَوْنَ إِلَىٰ قَوْمٍ أُو۟لِى بَأْسٍ شَدِيدٍ تُقَـٰتِلُونَهُمْ أَوْ يُسْلِمُونَ ۖ فَإِن تُطِيعُوا۟ يُؤْتِكُمُ ٱللَّهُ أَجْرًا حَسَنًا ۖ وَإِن تَتَوَلَّوْا۟ كَمَا تَوَلَّيْتُم مِّن قَبْلُ يُعَذِّبْكُمْ عَذَابًا أَلِيمًا
Say to those who remained behind of the bedouins, "You will be called to [face] a people of great military might; you may fight them, or they will submit. So if you obey, Allah will give you a good reward; but if you turn away as you turned away before, He will punish you with a painful punishment."
لَّيْسَ عَلَى ٱلْأَعْمَىٰ حَرَجٌ وَلَا عَلَى ٱلْأَعْرَجِ حَرَجٌ وَلَا عَلَى ٱلْمَرِيضِ حَرَجٌ ۗ وَمَن يُطِعِ ٱللَّهَ وَرَسُولَهُۥ يُدْخِلْهُ جَنَّـٰتٍ تَجْرِى مِن تَحْتِهَا ٱلْأَنْهَـٰرُ ۖ وَمَن يَتَوَلَّ يُعَذِّبْهُ عَذَابًا أَلِيمًا
There is not upon the blind any guilt or upon the lame any guilt or upon the ill any guilt [for remaining behind]. And whoever obeys Allah and His Messenger - He will admit him to gardens beneath which rivers flow; but whoever turns away - He will punish him with a painful punishment.