Musannaf Ibn Abi Shayba 26:436

Jarir narrated to us, from Mughira, from al-Sha'bi, who said: Ali gave a judgment regarding two men who had intercourse with a woman in one period of purity, and she gave birth. He judged that he (the child) should be shared between them; he inherits from them and they inherit from him, and he belongs to the one of them who had intercourse with her last.