In his book, Creatures of Habit, Pastor Steve Poe writes:

When I was in grade school several of the kids in the neighborhood walked to and from school each day. We walked down a street where a man had a large dog, a boxer. It had a very intimidating bark and was tethered to a long chain in the backyard. When we would walk past this house that dog would start barking and come running after us. Of course, the chain would eventually stop him, but we are were always worried that one day he would break loose and attack us. I would start worrying about that dog blocks before I ever reached the house.

One day the owner of the dog was in the yard and watched this entire scene unfold. The next day, as we walked by the house, the man was once again outside, only this time he had the dog on a leash. When he saw us, he began to motion for us to come over to him. We didn't know if we were in trouble or if he was going to let his dog bite us, but either way we were not walking over to him.

Then he started walking over to us. The entire time the man kept saying to us, "You don't need to be afraid of my dog." Then he knelt down and pulled back the dog's upper lip to reveal he had no teeth! Seriously, there was not a tooth in that dog's mouth. The man said, "Even if this dog were to ever get loose and try to bite you, it wouldn't hurt." All of us started to laugh. And we were never afraid of that dog again. When that man told us the truth, all of the fears and worries we had about that dog were instantly gone.

Possible Preaching Angle:

The most common tool in Satan's toolbox is to lie to us. Satan wants to bring worry and fear on you by whispering into your ear a whole lot of what-ifs about things that may not even be true. But what you will find is, like that dog, the devil has no teeth, and his bark is worse than his bite (John 8:44).