سَيَقُولُ الْمُخَلَّفُونَ إِذَا انطَلَقْتُمْ إِلَىٰ مَغَانِمَ لِتَأْخُذُوهَا ذَرُونَا نَتَّبِعْكُمْ ۖ يُرِيدُونَ أَن يُبَدِّلُوا كَلَامَ اللَّهِ ۚ قُل لَّن تَتَّبِعُونَا كَذَٰلِكُمْ قَالَ اللَّهُ مِن قَبْلُ ۖ فَسَيَقُولُونَ بَلْ تَحْسُدُونَنَا ۚ بَلْ كَانُوا لَا يَفْقَهُونَ إِلَّا قَلِيلًا
“Those who stayed behind will say, when you [believers] set out to take the spoils of war, "Let us accompany you." They wish to change Allah's promise. Say, [O Prophet,] "You will not accompany us. This is what Allah has said before." They will then say, "In fact, you are driven by jealousy against us!" The truth is: they can hardly comprehend.”
This ayah is part of Surah al-Fath, revealed -- as this event's own significance note states -- "concerning this incident" (Q48:1), the Treaty of Hudaybiyyah.