Sunan Ibn Majah, Chapter: The Book of the Sunnah

"Abu Laila used to travel with 'Ali, and he used to wear summer clothes in winter and winter clothes in summer. We said: 'Why don't you ask him (about that)?' He said: "The Messenger of Allah (saw) sent for me and my eyes were sore, on the Day of Khaibar. I said: 'O Messenger of Allah, my eyes are sore.' He put some spittle into my eyes, then he said: 'O Allah, take heat and cold away from him.' I never felt hot or cold again after that day. He [the Prophet (saw)] said: 'I will send a man who loves Allah and His Messenger, and whom Allah and His Messenger love, and he is not one who flees from the battlefield.' The people craned their necks to see, and he sent or 'Ali and gave it (the banner) to him." (Daif)