Musnad Ahmad 33:716

Yunus narrated to us, Hammad—meaning Ibn Zayd—narrated to us, from Ayyub, who said: I heard Mujahid saying, from Jabir ibn Abdullah, who said: "We went out with the Messenger of Allah (may Allah bless him and grant him peace), and we were saying: 'Labbayk for Hajj.' Then he commanded us, so we made it an Umrah."