Musnad Abu Ya'la al-Mawsili 3:333

Zuhayr narrated to us, Jarir narrated to us, from Mughirah, from Umm Musa, who said: I heard Ali saying: "I have neither suffered from ophthalmia nor a headache since the Messenger of Allah (may Allah bless him and grant him peace) wiped my face and spat into my eyes on the day of Khaybar, when he gave me the banner."