Musannaf Ibn Abi Shayba 1:671

671. Rawh ibn ‘Ubadah narrated to us, from Muhammad ibn ‘Abd al-Rahman al-‘Adani, who said: I heard Muhammad ibn ‘Ali saying regarding the person in a state of major ritual impurity (junub), if he wants to sleep, or eat, or drink: He should perform ablution (wudu) like his ablution for prayer.