Everything, every logic indicates god is only one without a second , neither he is a man nor anything which is comparable in this universe.
He is beyond human comprehension.
Every book was sent by God to us through his messengers (rishis) . but people used to corrupt those scriptures according to their tastes and their advantages and god sent another scripture to another prophet or messenger to correct corrupt scriptures but people who loved and respected their ancestors were not willing to abandon their ancestor’s faith neither they were willing to prove them wrong and many other hurdles , that’s why we find many religions with their own books suppose Torah were given to moses pbuh when it got corrupted another messenger was sent to same nation with revised scripture in which dos and donts were written again , that was Jesus pbuh after that this message also gt corrupted and then prophet Muhammad was sent with Quran and this is the last prophet and last revelation of God (Quran) same happened to Hindu scriptures but we have little record of them because they are very old scriptures but also corrupted but these Vedas also tell us that antim reshi will come whose name is clearly written as MUHAMMAD pbuh
(The praise worthy) slave of god.