What is the author name of life of Muhammad?

Answer 1

Ibn Ishaq is said to have compiled copious notes for a biography of Muhammad, but it is not known if he ever wrote the book. Unfortunately, none of his original notes have survived.

Ibn Hisham took some of Ibn Ishaq's notes, pretty well unchanged, and added a few notes of his own. This work is what we usually mean nowadays by "The Life of Muhammad".

Later a historian named Al-Tabari wrote a long history of all the prophets. For the sections on Muhammad, he also copied down many of Ibn Ishaq's notes, some of which contain new information, not included in the ones that Ibn Hisham copied.

Because both Ibn Hisham and Al-Tabari copied some sections of Ibn Ishaq identically, yet other sections of their works are quite different, we know that they did not copy each other or make things up, but that both honestly copied Ibn Ishaq.

An Englishman named Alfred Guillaume tried to reconstruct Ibn Ishaq's original supposed book by adding all Al-Tabari's unique sections to the Ibn Hisham book, then translating it all into English. (He also added Ibn Hisham's notes. But he did not include the non-Ibn Ishaq work that can be found in Tabari.)

You can read Guillaume's translation of the "Life of Allah's Messenger" for free by googling for it.