His complete biography has been authenticated and circulated amongst scholars around the world starting while he was still alive and continuing up until today. One of the first examples we quote from is from the Encyclopedia Britannica, as it confirms:

(Regarding Muhammad) ... a mass of detail in the early sources shows that he was an honest and upright man who had gained the respect and loyalty of others who were likewise honest and upright men. [Vol. 12]

Another impressive tribute to Muhammad, peace and blessings be upon him is in the very well written work of Michael H. Hart, The 100: A Ranking of the Most Influential Persons in History. He states that the most influential person in all history was Muhammad, peace and blessings be upon him, with Jesus second. Examine his actual words.....My choice of Muhammad to lead the list of the world's most influential persons may surprise some readers and may be questioned by others, but he was the only man in history who was supremely successful on both the religious and secular level.
[Michael H. Hart, THE 100: A RANKING OF THE MOST INFLUENTIAL PERSONS IN HISTORY, New York: Hart Publishing Company, Inc., 1978, page. 33.]

According to the Quran, Prophet Muhammad was the most excellent example for all of humanity. Even non-Muslim historians recognize him to be one of the most successful personalities in history. Read what the Reverend R. Bosworth-Smith wrote in Mohammed & Mohammedanism in 1946:

Head of the state as well as the Church, he was Caesar and Pope in one; but, he was pope without the pope's claims, and Caesar without the legions of Caesar, without a standing army, without a bodyguard, without a palace, without a fixed revenue. If ever any man had the right to say that he ruled by a Right Divine, it was Mohammad, for he had all the power without instruments and without its support. He cared not for dressing of power. The simplicity of his private life was in keeping with his public life.