Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) forbade intercourse with pregnant women until they give birth, and said: "(It is) another's crop." And he forbade selling the spoils of war before they are divided, eating domestic donkeys, and every fanged beast of prey.
This indicates that once they have been divided, selling them is permissible. The evidence for the permissibility of dividing them in dar al-harb (enemy territory) has already been given.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18304