if the mountain won't come to Muhammad

The earliest appearance of the phrase is from Chapter 12 of the Essays of Francis Bacon, published in 1625:

Mahomet made the people believe that he would call a hill to him, and from the top of it offer up his prayers, for the observers of his law. The people assembled; Mahomet called the hill to come to him, again and again; and when the hill stood still, he was never a whit abashed, but said, If the hill will not come to Mahomet, Mahomet will go to the hill.[1]

It was published in John Ray's 1670 book of English proverbs,[2][3] The more complete reading of the essay makes it clear that Sir Francis Bacon meant the example to be disparaging, as he refers to “…mountebanks for the natural body, so are there mountebanks for the politic body…" in the context of his discussion "of boldness", or what might be described in modern, political terms as brazening out a scandal or failure.

Though widely associated with Muhammad, the prophet of Islam who lived in Arabia in 6th century, there is no written or oral tradition that traces this phrase back to him. There is however, a phrase in Turkish, "Dağ sana gelmezse, sen dağa gideceksin…" ("If the mountain won't come to you, you must go to the mountain") that has no reference to Muhammad (an alternative version of which is to be found at Dağ yürümezse abdal yürür), known as one of the "atasözleri", or common sayings that exist in modern Turkish, but are thought to have much older origins.