to buy mom

A young boy went to a horse auction with his father.
He watched his father move from horse to horse, running his hands up and down the horse’s legs, rump, and chest.
After a few minutes, the boy asked, “Dad, why are you doing that?”
His father replied, “Because when I’m buying horses, I have to make sure that they are healthy and in good shape before I buy.” The boy, looking worried, said, “Dad, I think the postman wants to buy mom.”