Three Strikes

A farmer and his brand new wife were riding home from the chapel in a wagon pulled by a team of horses, when the older horse stumbled.
The farmer said, “That’s once.”
A little farther down the road the poor old horse stumbled again. The farmer said, “That’s twice.”
A little while later the horse stumbled yet again. The farmer didn’t say anything, but reached under the seat, pulled out a shotgun and shot the horse.
His brand-new wife yelled, telling him, “That was an awful thing to do.”
The farmer responded, “That’s once.”