Musnad Ahmad 1153:2323

Ya'qub narrated to us, he said: My father narrated to us, from Ibn Ishaq, he said: And Abd al-Rahman ibn al-Aswad ibn Yazid al-Nakha'i narrated to me, from his father, from Aisha, the wife of the Prophet, may God bless him and grant him peace. He said: I asked her how the Messenger of God would act if he were in a state of major ritual impurity (junub) and wanted to sleep before he performed the ritual bath (ghusl). She said: "He would perform his ablution (wudu) for prayer, then he would sleep."