Musnad Ahmad 7:13

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Yahya ibn 'Abbad ibn 'Abdullah ibn al-Zubayr narrated to me, from his father, from 'Abdullah ibn al-Zubayr, from al-Zubayr, who said: I heard the Messenger of Allah, may Allah bless him and grant him peace, say on that day: "Talhah has made [Paradise] obligatory," when he did for the Messenger of Allah, may Allah bless him and grant him peace, what he did. That is, when Talhah knelt down for him, and the Messenger of Allah, may Allah bless him and grant him peace, climbed onto his back.