MUHAMMAD IBN ISHAQ IBN YASAR IBN KHIYAR
born 704 A.D. (85 A.H.) in Medina and died d. 767 A.D. He was the earliest person to write the most comprehensive and most important biography of Muhammad, Sirat Rasullullah. What we have today is Ibn Hisham's recension, who died 60 years after Ibn Ishaq. Ibn Hisham said that he edited this biography and omitted certain details that were deemed too offensive to Muslims. Alfred Guillaume translated this edition into The Life of Muhammad and tried to reconstruct Ibn Ishaq's manuscript using quotations from other Muslim scholars. This biography provides one of the most important sources of Muhammad's life.
Ibn Ishaq was was criticized by theologians for being imprecise in naming his sources (which goes to show that the isnad was not an important part of the biographical traditions at his time. This is confirmed by looking at other writings around the same time. The role of the isnad gain prominence only about a century later during theological disputes between the various schools). More information can be found at "Ibn Ishaq" Britannica Online