Musannaf Ibn Abi Shayba 9:1667

Hushaym narrated to us, from Mughira and Ubayda, from Ibrahim, who said: "If he acknowledges the child, then it is not for him to disavow him." And Hammad said: "If he acknowledges the pregnancy, it is not for him to deny it, unless he wishes to say: 'I made a mistake regarding the waiting period (iddah).'"