I have a question about taking a newborn outside in the public?

Our child was born a few days ago and he just came home yesterday. Now, my girlfriend wants to take him out with us to go shop for furnite. My mom told me that she should not have the baby out in the public yet because the baby can be exposed to alot of things. Is this true? Is it ok for the baby to go with us shopping? Please someone give me the right answer