(9) باب مَنَاقِبُ عَلِيِّ بْنِ أَبِي طَالِبٍ الْقُرَشِيِّ الْهَاشِمِيِّ أَبِي الْحَسَنِ رضى الله عنه
Narrated Salama:
`Ali happened to stay behind the Prophet (ﷺ) and (did not join him) during the battle of Khaibar for he was having eye trouble. Then he said, "How could I remain behind Allah's Messenger (ﷺ)?" So `Ali set out following the Prophet (ﷺ) , When it was the eve of the day in the morning of which Allah helped (the Muslims) to conquer it, Allah's Messenger (ﷺ) said, "I will give the flag (to a man), or tomorrow a man whom Allah and His Apostle love will take the flag," or said, "A man who loves Allah and His Apostle; and Allah will grant victory under his leadership." Suddenly came `Ali whom we did not expect. The people said, "This is `Ali." Allah's Messenger (ﷺ) gave him the flag and Allah granted victory under his leadership.
Reference: Sahih al-Bukhari 3702
In-book reference: Book 62, Hadith 53
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 5, Book 57, Hadith 52