Musannaf Ibn Abi Shayba 9:1672

'Abdah narrated to us, from Sufyan, from Abu Ma'shar, from Ibrahim, regarding a man who acknowledges his child and then disowns him: He said, "He performs li'an (imprecation) according to the Book of Allah, and the child is attached [to him] by the judgment of the Messenger of Allah, peace and blessings of Allah be upon him."