Mark begins this book with the words that the prophet Isaiah wrote long ago about a messenger who would come and tell the people to get ready for the Lord's coming. Verses 4-15 show how this prophecy was fulfilled by John the Baptist and Jesus Christ.
Doing this represents preparing the people for the Lord's arrival. Alternate translation: "will prepare the people for your arrival" (See: [[rc://en/ta/man/translate/figs-metaphor]])