Musnad Ahmad 27:1847

Ya'la and Muhammad narrated to us, they said: Muhammad—meaning Ibn Ishaq—narrated to us, Nafi' narrated to me, from Ibn Umar, who said: "The Messenger of Allah (ﷺ) forbade the sale of *gharar* (uncertainty/risk)." And he said: "The people of the Jahiliyyah (pre-Islamic era) used to conduct that sale; a man would purchase [an animal] for the *habal al-habalah* (the fetus of the fetus), so the Messenger of Allah (ﷺ) forbade it." Muhammad ibn 'Ubayd said in his narration: "The *habal al-habalah*, so the Messenger of Allah (ﷺ) forbade that."