The Devil and his Grandmother
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It is Aarne-Thompson type 812, the devil's riddle.
Three soldiers could not live on their pay, and so attempted to desert by hiding in a cornfield. When the army did not march away, they were soon caught between starving or emerging to face execution. A dragon happened to fly by at this time, however, and offered the three men salvation under the condition that they must serve him for seven years. When they agreed, the dragon carried them off. However, the dragon was in fact the Devil. He gave them a whip with which they could make money, but said at the end of seven years, they were his unless they could guess a riddle in which case they would be free and could keep the whip.
At the end of the seven years, two of the soldiers were morose at the thought of their fate. An old woman advised them to go down to a cottage for help. The third soldier, who did not fear the riddle, went down and met the devil's grandmother. She was pleased with his manners and hid him in the cellar. When the devil came, she questioned him, and the soldier learned the answers.
The Devil found them at the end of the seven years, and said he would take them to hell and serve them a meal. The riddle was: what was the meat, the silver spoon, and the wineglass for that meal. The answers were a dead sea-cat in the North Sea, a whale rib, and an old horse's hoof.
In the end, the soldiers escaped and kept the whip.