Matthew 3:3 meaning

The parallel accounts of this prophetic fulfillment are found in Mark 1:3, Luke 3:3-6, John 1:23.

Verse 3 contains the sixth direct prophecy Matthew cites as being fulfilled, offering it as proof that Jesus is the Kingly Messiah. John, according to Matthew, is the voice of one crying in the wilderness. He is the prophetic herald who warns everyone to "Make ready the way of the LORD, Make His paths straight!" (v 3). This voice announces the coming of the LORD and heeds everyone to make ready and prepare the way.

Matthew only quotes the first lines of this prophecy. Many Jews would instantly recognize this passage and be able to complete the rest by heart. Isaiah's prophecy continues:

"A voice is calling,
'Clear the way for the Lord in the wilderness;
Make smooth in the desert a highway for our God.
'Let every valley be lifted up,
And every mountain and hill be made low;
And let the rough ground become a plain,
And the rugged terrain a broad valley;
Then the glory of the Lord will be revealed,
And all flesh will see it together;
For the mouth of the Lord has spoken.'"
(Isaiah 40:3-5)

The message is similar to John's words from the previous verse: "Repent, for the Kingdom of Heaven is at hand."

Both announce a divine arrival:
"Clear the way for the Lord"
"The Kingdom of Heaven is at hand."

Both give a call to action and change:
"Clear the way."
"Make smooth."
"Repent."

Both allude to an upheaval of the status quo. In particular, the political status quo is about to be capsized:

"Let every valley be lifted up,
And every mountain and hill be made low;
And let the rough ground become a plain,
And the rugged terrain a broad valley"
"The Kingdom of Heaven is at hand."

Being in the wilderness of Judea when he proclaims his message further associates John with this prophecy.