Musnad Abu Ya'la al-Mawsili 109:23

Ishaq narrated to us, Sufyan narrated to us, from Ibn al-Munkadir, who heard Jabir saying: The Messenger of Allah (may Allah bless him and grant him peace) called upon the people on the day of the Trench, and al-Zubayr volunteered. Then he called upon the people, and al-Zubayr volunteered. The Messenger of Allah (may Allah bless him and grant him peace) said: "Every prophet has a disciple (hawari), and my disciple is al-Zubayr."