(Al-Anfal) 8 : 67
مَا كَانَ لِنَبِيٍّ أَنْ يَكُونَ لَهُ أَسْرَىٰ حَتَّىٰ يُثْخِنَ فِي الْأَرْضِ ۚ تُرِيدُونَ عَرَضَ الدُّنْيَا وَاللَّهُ يُرِيدُ الْآخِرَةَ ۗ وَاللَّهُ عَزِيزٌ حَكِيمٌ
It is not suitable for a Prophet that he has captives of war until he has thoroughly subdued the land; you are preferring the gains of this world while Lord Allah is preferring the gains of the Hereafter, and Allah is Exalted, the Wise.