Although I like this puzzle, I'm still fairly new to this site and I've never tried to write one like this before. I think it may be a little too long, a bit too easy and some of the spelling and/or wording may need tweaking. Consider me open to suggestions!
A man and his sons are traveling east to west across a desert in dizzying heat when they come to an oasis where a djinni, a marid and an oracle stand. The father asked permission for his sons to drink from the oasis and top up their water. The marid, the leader of the three, refused this request; but for his own amusement he offers a drink from the oasis and a single wish to be granted to any man who can, without any help from his companions, pass a test of wisdom, strength, skill or cunning in a manner of their choosing.
The father stood silently as his youngest son, perhaps the greatest archer that had ever lived, stepped forward. The oracle spoke the words "I have seen the outcome of every test and in only one could you win your wish". The archer proposes a challenge of archery, thinking that surely his greatest talent must be the test that can win him his wish. The marid said to the archer "Loose three arrows and if even one can touch my shadow from where you now stand you will have your wish." The archer stood for a moment shocked by his luck. He had surely been underestimated. He readied his first arrow and loosed at the shadow, ten yards or so away. A clattering was heard as two arrows fell to the ground away from the shadow. The djinni, who now held a bow, had struck the archer's arrow from the air with his own. After a moment of stunned silence, the archer lined up his next shot and waited, watching the djinni, who simply held his bow and a single arrow in either hand and did not move. The archer loosed his arrow and the djinni moved like lightning, and again two arrows clattered to the sands away from the shadow. The djinni lowered his bow, shrugged and turned away looking something between smug and bored. The archer who was quick on the draw took the advantage and loosed another arrow in a flash, before the djinni turned round, but again, like lightning the djinni flinched and two arrows clattered to the floor away from the shadow of the marid. "I must have chosen poorly" said the archer.
The second son, a wise cracking joker, stepped forward. The oracle spoke the words once more "I have seen the outcome of every test and in only one could you win your wish". The joker proposed a guessing game. The marid reached down, plucked a small mound of sand and placed it in his open palm. Then he said to the joker "Within three tries, guess correctly how many grains of sand are in my hand and you will have your wish." Three guesses the joker makes and each time the marid shakes his head. "I must have chosen poorly" said the joker.
The third and final son, a strong warrior, and steady as a rock, stepped forward. Again the oracle spoke the words "I have seen the outcome of every test and in only one could you win your wish". The warrior, proposes a test of strength and balance, for he was well suited to such tasks. The marid walked down the steep bank to the crystal clear oasis waters and filled a large wooden bowl right up to the brim. Then he said to the man "Within three tries, carry this bowl back up the bank to my companions without spilling a single drop and you will have your wish." Wasting no time, the warrior walked down the bank and assessed the bowl. He chose his stance and his grip and slowly began to lift. As he did, a trickle of water breached the edge and escaped to the sands. The marid shook his head and re-filled the bowl to his liking. Full of determination, the warior tried again, going even more slowly than before, and this time, he was able to lift the bowl to his chest, but as he took the first step, the water rocked and spilled a drop down onto the sand. The marid reset the bowl and the warrior stood thinking for a moment. He smiled as an idea popped into his head. He crouched by the bowl and positioned himself to sip at the water. "No!" said the marid. "You may not drink until you have completed the task." Though disappointed, with all his concentration and focus, he made his third attempt and was able to walk a few steps with barely a ripple appearing upon the water's surface, but as he climbed the bank a tiny slip on the sand sent a trickle over the edge and again the drops fell from the bowl to the sand. "I must have chosen poorly" said the warrior.
The father stepped forwards looking annoyed. He was old and in his age he had become slow and weak, and his senses dull, and yet now the oracle remained silent. "Let me face a test of teaching and I will win my wish." he said. "Very well." spoke the marid "Each man will be given one more chance at their test and each man must pass, and you may speak only a single word to each of them." The father stood silent for a few more moments before turning to his sons and speaking a the same, rather angry word three times. Then the sons began their tasks. The archer nocked and fired a single arrow and into the shadow of the marid it went; the joker made a single guess and his answer was correct; The warrior carefully carried the bowl of water up the bank without spilling a single drop.
What word did the father speak to his sons? And just for fun, what might his wish have been?
Also, a slightly bigger and shinier than usual +1 to whomever can tell me why the oracle says "in only one could you win your wish."