A farmer and his brand new bride 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 further along, the poor old horse stumbled again.
The farmer said, "That's twice."

After a little, while the poor old horse stumbled again. The farmer didn't say anything, but reached under the seat, pulled out a shotgun and shot the horse.
His brand new bride raised all kind of hell with him, telling him, "That was an awful thing to do."

The farmer said, "That's once."