Musnad Ahmad 31:796

Ibn Abi ‘Adi narrated to us, from Sa‘id, from Qatadah, from Salih Abu al-Khalil, from Abu ‘Alqamah, from Abu Sa‘id al-Khudri: "The companions of the Messenger of Allah (may Allah bless him and grant him peace) took female captives on the day of Awtas who had husbands among the polytheists. Some of the companions of the Messenger of Allah (may Allah bless him and grant him peace) refrained and considered it sinful to have intercourse with them. He said: So this verse was revealed regarding that: 'And [also prohibited to you are] all married women except those your right hands possess' [An-Nisa: 24]."