It is not for a Prophet that he should have prisoners of war (and free them with ransom) until he had made a great slaughter (among his enemies) in the land. You desire the good of this world (i.e. the money of ransom for freeing the captives), but Allah desires (for you) the Hereafter. And Allah is All-Mighty, All-Wise." (8:67)

O Prophet! Say to the captives that are in your hands: "If Allah knows any good in your hearts, He will give you something better than what has been taken from you, and He will forgive you, and Allah is Oft-Forgiving, Most Merciful."" (8:70)