Musnad Ahmad 1153:758

Surayj narrated to us, Abu 'Awanah narrated to us, from Qatadah, from Zurarah ibn Awfa, from Sa'd ibn Hisham, from 'Aishah: "That the Messenger of Allah (peace and blessings of Allah be upon him), when his eyes overcame him, or he was in pain, and he did not pray at night, he would pray twelve rak'ahs during the day."