They walked for miles and miles looking for a gas station. They finally came to a
doctor's office, entered and asked where they might be able to purchase some gas.
He told them he had a tank in the back and would gladly give them some gas, but he didn't have a can to carry it back to the car. He did however offer them the only thing he had: a bed pan.
They took the bed pan back down the road to their car and proceeded to pour the gas into the tank.
In the mean time a preacher was driving down the road and was puzzled at what he saw. The nuns were pouring the gas from the bedpan into the tank.
He replied as he stopped his car: "I have never seen that work, but, boy!, I do admire your faith".