Sahl bin Saad reported,

The Messenger of Allah ﷺ said, "Tomorrow I will give the banner to a man through whose hands Allah will grant victory."The people spent the night discussing among themselves which of them would be given it. When morning came, they all went to the Messenger of Allah ﷺ, each hoping to be the one given the banner.He asked, "Where is Ali bin Abu Talib?"They replied, "Messenger of Allah, he is suffering from pain in his eyes."He said, "Send for him and bring him to me."When Ali was brought, the Prophet ﷺ spat into his eyes and prayed for him, and he was healed as though he had never been in pain. The Prophet ﷺ then gave him the banner.Ali asked, "Messenger of Allah, shall I fight them until they become like us?"He answered, "Proceed at ease until you reach their territory, then call them to Islam and inform them of what is required of them from the rights of Allah. By Allah, if Allah guides a single man through you, that is better for you than possessing red camels."

Bukhari 3701

Sahih

حدثنا قتيبة بن سعيد حدثنا عبد العزيز عن أبي حازم

عن سهل بن سعد رضي الله عنه

أن رسول الله ﷺ قال لأعطين الراية غدا رجلا يفتح الله على يديه قال فبات الناس يدوكون ليلتهم أيهم يعطاها فلما أصبح الناس غدوا على رسول الله ﷺ كلهم يرجو أن يعطاها فقال أين علي بن أبي طالب فقالوا يشتكي عينيه يا رسول الله قال فأرسلوا إليه فأتوني به فلما جاء بصق في عينيه ودعا له فبرأ حتى كأن لم يكن به وجع فأعطاه الراية فقال علي يا رسول الله أقاتلهم حتى يكونوا مثلنا فقال انفذ على رسلك حتى تنزل بساحتهم ثم ادعهم إلى الإسلام وأخبرهم بما يجب عليهم من حق الله فيه فوالله لأن يهدي الله بك رجلا واحدا خير لك من أن يكون لك حمر النعم

البخاري 3701صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Virtues of the companions of the Prophet ﷺ
Chapter
Virtues of Ali bin Abu Talib Qurashi Hashimi, Abu Hasan, may Allah be pleased with him
Numbering
Darussalam 3701
Bukhari 3701