Musnad Ahmad 33:779

Aswad ibn Amir narrated to us, Abu Bakr informed us, from al-A’mash, from Abu Sufyan, from Jabir ibn Abdullah, who said: We were with the Prophet, peace and blessings of Allah be upon him, on a military expedition. He said: I sought permission to hasten [my return], and I said: "I have married." He said: "A previously married woman or a virgin?" I said: "A previously married woman." He said: "Why not a virgin, so that you might play with her and she might play with you?" He said: "Go and do a wise deed." Abu Bakr said: "Meaning, do not come upon them [your wives] by night."