Why he did that, doesn’t that make his position as an Apostle weak in front of everyone!, in the past and nowadays, if he was sure that he is God’s messenger, shouldn’t he insist on his position despite everything else!
**Sahih Bukhari, Book 50, Volume 3, Number 891: **
"…Suhail said to the Prophet “Please conclude a peace treaty with us.” So, the Prophet called the clerk and said to him, “Write: By the Name of Allah, the most Beneficent, the most Merciful.” Suhail said, “As for ‘Beneficent,’ by Allah, I do not know what it means. So write: By Your Name O Allah, as you used to write previously.” The Muslims said, “By Allah, we will not write except: By the Name of Allah, the most Beneficent, the most Merciful.” The Prophet said, “Write: By Your Name O Allah.” Then he dictated, “This is the peace treaty which Muhammad, Allah’s Apostle has concluded.” Suhail said, "By Allah, if we knew that you are Allah’s Apostle we would not prevent you from visiting the Kaba, and would not fight with you. So, write: “Muhammad bin Abdullah.” The Prophet said, "By Allah! I am Apostle of Allah even if you people do not believe me. Write: Muhammad bin Abdullah…"