Sahih al-Bukhari 2942

'Abdullah ibn Maslama al-Qa'nabi narrated to us; 'Abd al-'Aziz ibn Abi Hazim narrated to us from his father, from Sahl ibn Sa'd (may Allah be pleased with him), who heard the Prophet (ﷺ) say on the day of Khaybar: ‘I will give the banner to a man through whose hands Allah will grant victory.’ The people stood hoping to be the one who would receive it. The next morning, each of them still hoped to receive it. He said, ‘Where is 'Ali?’ It was said, ‘His eyes are hurting.’ So he ordered that 'Ali be brought. He spat into his eyes, and he recovered on the spot as though he had never had any ailment. He said, ‘We will fight them until they become like us.’ He replied, ‘Proceed calmly until you reach their territory. Then invite them to Islam and tell them what is required of them. By Allah, if even one man is guided through you, that is better for you than red camels.’