The phrase if the mountain will not come to Mahomet ¹, Mahomet must go to the mountain, and its variants, have several meanings—in particular:
– if someone whom you want to see does not come to you, you must go to them;
– if you cannot get or do what you want, you must settle for what you can get or do and be satisfied with it;
– if one party in a negotiation or dispute will not concede a point, the other party will have to compromise or there will be deadlock.

¹ In this phrase, Mahomet represents an inaccurate rendering of the Arabic name Muḥammad, borne by the founder of the religion of Islam (c.570-632).

David Wright, writing from Houston, Texas, USA, used the phrase punningly in the Daily Mirror (London, England) of Friday 12^th November 1971:

Mathis ² pulled his 23 stone self together and made up his mind that after two years of self-imposed, self-searching, lonely exile, it was time to return to the ring.
Next Wednesday, in the great Astrodome Stadium here, boxing’s Mountain will come to Muhammad.
Mathis, 6ft. 3in., and “slimmed” down to a few pounds under 19st., will attempt to whip Cassius Clay Muhammad Ali ³.

² Buster Mathis (1943-1995) was a U.S. boxer.
³ Muhammad Ali (born Cassius Marcellus Clay – 1942-2016) was a U.S. boxer.

The phrase if the mountain will not come to Mahomet, Mahomet must go to the mountain originated in a story (of unknown origin) told by the English philosopher and statesman Francis Bacon (1561-1626) in Of Boldnesse, published in The Essayes or Counsels, Ciuill and Morall, of Francis Lo. Verulam, Viscount St. Alban (London: Printed by Iohn Haviland for Hanna Barret, 1625):

You shall see a Bold Fellow, many times, doe Mahomets Miracle. Mahomet made the People beleeue, that he would call an Hill to him; And from the Top of it, offer vp his Praiers, for the Obseruers of his Law. The People assembled; Mahomet cald the Hill to come to him, againe, and againe; 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. So these Men, when they haue promised great Matters, and failed most shamefully, (yet if they haue the perfection of Boldnesse) they will but slight it ouer, and make a turne, and no more adoe.

The earliest occurrences of the phrase if the mountain will not come to Mahomet, Mahomet must go to the mountain, and variants, that I have found are from the following two texts:

1-: From Θεομαχία Ἀυτεξουσιαστικη [Theomakhía Autexousiastikē]: Or, A Display of Arminianisme (London: Printed by I. L. for Phil. Stephens, 1643), by the English theologian John Owen (1616-1683):

[The Arminians] will scarse obtaine so prosperous an issue of their endeavour, as Mahomet had, when he promised the people, he would call a mountaine unto him: which miracle when they assembled to behold, but the mountaine would not stirre for all his calling, he replyed, if the mountaine will not come to Mahomet, Mahomet will goe to the mountaine, and away he packed towards it, but we shall finde that our Arminians, can neither themselves, climbe the high mountaine of innocency, nor yet call it down, into the valley of sinne and corruption, wherein they are lodged.

2-: From The Wisdom of God manifested in the Works of the Creation (London: Printed for Samuel Smith, 1692), by the English naturalist and theologian John Ray (1627-1705):

Let Matter be divided into the subtilest parts imaginable, and these be moved as swiftly as you will; it is but a sensless [sic] and stupid Being still, and makes no nearer approach to Sense, Perception, or vital Energy than it had before; and do but only stop the internal Motion of its parts and reduce them to Rest, the finest and most subtile Body that is may become as gross, and heavy, and stiff as Steel or Stone. And as for any external Laws or established Rules of Motion, the stupid Matter is not capable of observing or taking any notice of them; but would be as sullen as the Mountain was that Mahomet commanded to come down to him, neither can those Laws execute themselves.