Musannaf Ibn Abi Shayba 9:1527

Abu Bakr narrated to us, he said: Yahya ibn Sa'id narrated to us, from Sufyan, from al-A'mash, from Muslim, from Masruq, who said: When a woman would go to the polytheists, they would give her husband the equivalent of her dowry. And when she would go to a people among the polytheists with whom there was no treaty between them and [the Muslims], then: "If you have an opportunity [and you have seized the spoils from the enemy], then give to those whose wives have gone the equivalent of what they had spent." He says: Give her husband from the spoils the equivalent of her dowry.