Musannaf Ibn Abi Shayba 1:821

821. Ishaq al-Azraq narrated to us, from Hisham, from al-Hasan, regarding the man who is in a state of major ritual impurity (junub) who goes to attend to a need and goes to the market. He said: He should wash his private parts and perform ablution (wudu) like his ablution for prayer.