All of the provisions which God made with Israel were made for the ultimate benefit of the whole earth. This required the coming of a Messiah to offer the supreme sacrifice for sin; once for all; however, to preserve the world until that time, it was necessary to preserve the belief in the one true God.
This could be a difficult task when the whole world was creating gods of every description. It would best be achieved by the selection of one people, their separation from others, and their continued segregation. Such a people would need a definite constitution, the basic laws of which would be, “Thou shall have no other gods before me.” In that way they could be called back to their original purpose when they wandered from it.
Accordingly, when every nation had chosen their gods, the God of Heaven chose one nation. As a preparatory step, He went to the land of Caldea and called a man whose father and grandfather were already idolaters (Joshua 24:2).
Taken from the book
ROYAL PRIESTHOOD, pg. 31