Level 8 riddle

A wealthy Arab sheik has 2 sons that bicker and fight all the time. They hate each other and will not do anything for each other. They will not have anything to do with each other. He is so mad he decides to get back at them. He will not divide his wealth evenly between the 2 sons when he dies. They will probably fight over their rightful share anyway. He figures, "I must get them to at least do one thing for each other in their lifetime."
So he leaves a will behind saying, "the son whose camel reaches Mecca last inherits everything."

The next day, the 2 sons were in the desert, starting off the race, when they went:

"You go ahead, I have to have eat first"
"No, you go ahead, I have to go fetch some water"
"After you"
"No, it's OK, after you"

So they decide to start the race anyway, and try to trick the other one into reaching Mecca first.

3 days later, they are running out of water, and still going:

"You first"
"No, you first"

Then they see a caravan drawing near. The convoy is run by a wise man. He says, "what the hell are you guys doing, you're going to die here if you don't get where you're going soon".

So they tell him about their dilemma. After hearing their story he laughs so hard he is almost rolling on the floor. The 2 sons look at each other puzzled.

The wiseman catches his breath and says 2 words to them. Suddenly, the 2 sons get to the camels and dash for Mecca as fast as they can.

What were the 2 words?

Hints: The 2 words work in pretty much any language, it's not a grammtical thing, it's so easy even a child could know them.

Hints: No, it wasn't "fuck off!"

Hints: The father really did die and leave the will, the Wise man haddn't met any of them before.