Lawn Mower
This preacher was looking for a good used lawnmower one day. He found one at a yard sale that Little Johnny happened to be manning.
"This mower work, son?" the preacher asked.
Little Johnny said, "Sure does...just pull on the cord hard, though."
The preacher took the mower home and when he got ready to mow he yanked and pulled and tugged on that cord. Nothing worked. It wouldn't start.
Thinking he'd been swindled, he took the mower back to Little Johnny's house. "You said this would work if I pulled on the cord hard enough."
"Well," Johnny said, "you need to cuss at it sometimes."
The preacher was aghast. "I've not done that in years!"
"Just keep yanking on that cord, Preacher. It'll soon come back to you."