Musnad Ahmad 32:858

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, and Hajjaj said: Shu'bah narrated to me, he said: I heard Qatadah narrating from Anas ibn Malik, from the Prophet, peace and blessings of Allah be upon him, that he said: "None of you believes until he loves for his brother—or his neighbor—what he loves for himself." And Hajjaj did not express doubt.