Musnad Ahmad 2:144

Ya'qub narrated to us, my father narrated to us, from Muhammad ibn Ishaq, al-Zuhri narrated to me, from Sa'd Abu 'Ubayd, the freed slave of 'Abd al-Rahman ibn Azhar, who said: I witnessed the 'Eid with 'Umar ibn al-Khattab... then he mentioned the hadith.