Musannaf Ibn Abi Shayba 1:712

Ibn 'Uyaynah narrated to us, from 'Ubayd Allah ibn Abi Yazid, who heard Ibn 'Abbas saying: "A *sa'* [of water] is sufficient for the one who is in a state of *janabah* (major ritual impurity)." 'Ubayd Allah said: "I do not know whether [this is] before the *wudu'* or after it."