Close Reading

Lets go by what you say and i agree to it that it is in the quran about 4 witnesses.Now without these witnesses no one would believe what this woman said. Does not this same thing apply to mohammad: he married a 6 year old and said god/gabriel told him to do so, he married his daughter in law and said god/gabriel told him to do so, he led wars and said god/gabriel told him to do so...now who are the 4 witnesses to when ever mohd. heard or spoke to God, where are his witnesses, how to believe him