The proverbial phrase ‘If the mountain will not come to Muhammad…’ means that , if one’s will does not prevail, one must submit to an alternative.

The full phrase ‘If the mountain will not come to Muhammad, then Muhammad must go to the mountain’ arises from the story of Muhammad, as retold by Francis Bacon, in Essays, 1625:

Mahomet cald the Hill to come to him. And when the Hill stood still, he was neuer a whit abashed, but said; If the Hill will not come to Mahomet, Mahomet wil go to the hil.