Sahih Muslim — The Book of the Merits of the Companions — Hadith No: 6224
Translation
Salama b. Akwa' reported that it was 'Ali whom Allah's Apostle (ﷺ) left behind him (in the charge of his family and the Islamic State) on the occasion of the campaign of Khaibar, and his eyes were inflamed and he said:Is it for me to remain behind Allah's Messenger (ﷺ)? So he went forth and rejoined Allah's Apostle (ﷺ) and on the evening of that night (after which) next morning Allah granted victory. Allah's Messenger (ﷺ) said: I will certainly give this standard to a man whom Allah and His Messenger love. or he said: Who loves Allah or His Messenger and Allah will grant him victory through him, and, lo, we saw 'Ali whom we least expected (to be present on that occasion). They (the Companions) said: Here is 'Ali. Thereupon Allah's Messenger (may peace be upon hin) gave him the standard. Allah granted victory at his hand