Owner didn't expect that and saved his finger in a fraction of a second.

This video is the perfect example of why you should not disturb your pets when they are sleeping.
Here a Labrador of 7 years old is sleeping on the floor near his owner. The owner thought to have some fun by placing the treat on his mouth while the dog was sleeping.
Normally his dog doesn’t react to anything while sleeping But this time the things went the other way. Thankfully the owner’s hand was safe after this.
Labradors are known for their love. They hardly attack first but when they are sleeping they can bite like other dogs but I am sure that the moment they will come into the consciousness they will stop biting and start loving again.
In this case, it was the involuntary reaction of this dog. Normally they do it when any fly sits on the face.
As you can see the owner tried to put the treat very slowly it might have created the same sense of feeling on the surface and the dog reacted that way.