Musnad Ahmad 33:659

Hujayn and Yunus narrated to us, they said: Al-Layth ibn Sa'd narrated to us, from Abu al-Zubayr, from Jabir: "That when they were present with the Messenger of Allah (may Allah bless him and grant him peace) in Medina, and he sent the sacrificial animals (al-hady), whoever among us wished entered into ihram, and whoever wished refrained."