Al-Anfal - 8:67

مَا كَانَ لِنَبِيٍّ أَن يَكُونَ لَهُ أَسْرَى حَتَّى يُثْخِنَ فِي الأَرْضِ تُرِيدُونَ عَرَضَ الدُّنْيَا وَاللّهُ يُرِيدُ الآخِرَةَ وَاللّهُ عَزِيزٌ حَكِيمٌ
[8:67]
It is not fit for a prophet that he should take captives unless he has fought and triumphed in the land; you desire the frail goods of this world, while Allah desires (for you) the hereafter; and Allah is Mighty, Wise.
It is not fitting for a prophet that he should have prisoners of war until he hath thoroughly subdued the land. Ye look for the temporal goods of this world; but Allah looketh to the Hereafter: And Allah is Exalted in might, Wise.
It is not for any prophet to have captives until he hath made slaughter in the land. Ye desire the lure of this world and Allah desireth (for you) the Hereafter, and Allah is Mighty, Wise.