Salama bin Akwa reported,

Ali had stayed behind from the Prophet ﷺ at Khaybar because he was suffering from an eye ailment. Then he said, "Am I to stay behind from the Prophet ﷺ?" So he went and joined him.On the night before Khaybar was conquered, the Prophet ﷺ said, "Tomorrow I will surely give the banner to a man," or, "Tomorrow the banner will surely be taken by a man whom Allah and His Messenger love, and Allah will grant victory through him."We were all hoping for it. Then it was said, "Here is Ali." So he gave it to him, and Allah granted victory through him.

عن سلمة بن الأكوع، قال

كان علي- رضي الله عنه- تخلف عن النبي ﷺ في خيبر، وكان رمدا، فقال: أنا أتخلف عن النبي ﷺ؟ فلحق به، فلما بتنا الليلة التي فتحت، قال: الأعطين الراية غدا- أوليأخذن الراية غدا- رجل يحبه الله ورسوله، يفتح عليه فنحن نرجوها، فقيل هذا علي، فأعطاه، ففتح عليه.