It was narrated from al-Qasim that Abu Umamah said:

A man among the Muslims granted protection to a man when Abu ‘Ubaidah bin al-Jarrah was in charge of the army, Khalid bin al-Waleed and "Amr bin al-"As said: You should not acknowledge his protection. But Abu "Ubaidah said. We will grant him protection, I heard the Messenger of Allah (ﷺ) say: “One of the Muslims may grant protection and it is binding upon all the Muslims."