Musannaf Ibn Abi Shayba 1:939

Waki’ narrated to us, from Mis’ar, from Ma’bad ibn Khalid, from Ali, and from Ghalib Abu al-Hudhail, from Ibrahim, from Ali, who said: "When the circumcision [of the man] passes the circumcision [of the woman], then Ghusl (ritual bathing) has become obligatory."