Some dogs might take to walking with a leash as if they were born with one attached to their collar. There are always the few that freak out and try to lay down when a leash is being used to guide them. I had a puppy that would actually throw herself upside down, forcibly, each time I tried to get her to walk with a leash on. Thankfully we worked through this fiasco! Leave the leash attached to your dog in the house and monitor his behavior. Soon he will learn that if the leash is in your hand, he gets to go for a walk.