Musnad Abu Ya'la al-Mawsili 116:23

Ahmad narrated to us, Shababa narrated to us, Shu'bah narrated to us, from Qatadah, from Anas bin Malik, from 'Ubadah bin as-Samit, from the Prophet (peace and blessings of Allah be upon him), who said: "Indeed, the dream of a Muslim is one part of forty-six parts of prophethood."