Dear lilian,
One day the people ask to Mohammad "Do you have a wonder like the other prophets ?" and he says "yes" and he calls the mountain "come to me". Ofcouse it dosen't come and he says "when the mountain dosen't come to Muhammad than Muhammad goes to the mountain.".
Therefore the real text has to be like this.
Dear merdogan, sayings and proverbs are sometimes rendered into the many languages using different wordings.
This one in English reads like that or the other way round.
I don't think it should be 'must' here, because there's no such thing as 'must' in the original? I think that the translation before it was edited is correct..