The Prophet (ﷺ) went out in the company of 1300 to 1500 of his companions in the year of Al-Hudaibiya, and when they reached Dhul-Hulaifa, he garlanded and marked his Hadi and assumed the state of Ihram.
Sahih al-Bukhari Book 64, Hadith 201
← Previous Hadith Who was among those (who had given the Pledge of allegiance) under the Tree: Pious people will die in succession, and there will remain the dregs of society who will be like the useless residues of dates and barley and Allah will pay no attention to them.

Sahih al-Bukhari Book 64, Hadith 200 Next Hadith → That Allah's Messenger (ﷺ) saw him with the lice falling (from his head) on his face. Allah's Messenger (ﷺ) said, "Are your lice troubling you? Ka`b said, "Yes." Allah's Messenger (ﷺ) thus ordered him to shave his head while he was at Al-Hudaibiya. Up to then there was no indication that all of them would finish their state of Ihram and they hoped that they would enter Mecca. Then the order of Al-Fidya was revealed, so Allah's Messenger (ﷺ) ordered Ka`b to feed six poor persons with one Faraq of food or slaughter a sheep or fast for three days.

Sahih al-Bukhari Book 64, Hadith 202