Sahih Bukhari Volume 005, Book 059, Hadith Number 520.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 59. Military Expeditions Led by the Prophet (PBUH) (Al-Maghaazi)
Narrated By Salama : Ali remained behind the Prophet during the Ghazwa of Khaibar as he was suffering from eye trouble. He then said, "(How can) I remain behind the Prophet ," and followed him. So when he slept on the night of the conquest of Khaibar, the Prophet said, "I will give the flag tomorrow, or tomorrow the flag will be taken by a man who is loved by Allah and His Apostle , and (Khaibar) will be conquered through him, (with Allah's help)" While every one of us was hopeful to have the flag, it was said, "Here is 'Ali" and the Prophet gave him the flag and Khaibar was conquered through him (with Allah's Help).