What Is a Genuine Baptism?

In the baptist approach, why is it that one has to have faith? And why does it not count if some one doesn't really believe, or if it's is not a genuine baptism. Or if you are baptized prior to faith, and then come to faith later,. Why is it that you have re baptized if you already had it done to that not count? And here it is. It meaning baptism is an act of obedience, an act of human obedience. So it symbolizes our faith. In order to be a genuine baptism in this approach,  this is exactly what the argument confession is saying, is not the purpose of the sacraments. Is not the only