Musannaf Ibn Abi Shayba 9:1324

Affan narrated to us, he said: Hammad bin Salamah narrated to us, from Muhammad bin Ishaq, from Muhammad bin Ibrahim, from Salamah bin Abi Tufayl, from Ali, that the Prophet, peace and blessings of Allah be upon him, said: "O Ali, you have a treasure in Paradise, and you are the possessor of its two horns. So do not follow a glance with a glance, for you have the first [glance], but you do not have the last [glance]."