Musannaf Ibn Abi Shayba 3:1552

Jarir narrated to us, from Qabus, from his father, from Aisha, who said: "As for that which he did not abandon, neither when healthy nor when sick, neither while traveling nor while at home, neither when absent nor when present—meaning the Prophet (peace and blessings of Allah be upon him)—it is the two rak'ahs before the dawn."