Luke explicitly quotes Isaiah 40 and extends the quotation through 'all flesh shall see the salvation of God,' making preparation for the Lord and universal salvation programmatic for Luke-Acts.

Luke 1 has already framed John in Malachi's Elijah-forerunner language; Luke 3 now identifies his wilderness ministry through Isaiah 40. Canonical sequencing evidence: Luke joins Malachi’s forerunner portrait to Isaiah’s wilderness-way text as John’s public ministry begins.

John’s ministry at the Jordan naturally resonates with Israel’s earlier Jordan crossings and covenant-renewal memories, including Joshua 3–4, but Luke does not explicitly invoke Joshua or present John’s baptism as a fulfillment of that event.

When temple leaders challenge Jesus’ authority, Jesus explicitly turns the question to John’s baptism—whether it was from heaven or from men—linking their response to the forerunner with their challenge to Jesus.