In John 3:28, John the Baptist reiterates that he is not the Christ but sent before him, echoing his self-identification as the voice crying out.

Isaiah 40:3-5 is the original prophecy John quotes — God's command to prepare the way in the wilderness.

Matthew 3:3 directly quotes Isaiah 40:3 and applies it to John the Baptist, confirming the same prophecy John cites.

Mark 1:3 also quotes Isaiah 40:3 about John, showing the consistent Gospel identification of John as the wilderness voice.

Luke 1:17 says John will go before the Lord in Elijah's spirit to prepare hearts, directly matching the 'prepare the way' mission.

Luke 1:76-79 prophesies John as the prophet going before the Lord to prepare his ways, expanding on the same forerunner role.

Luke 3:4-6 quotes Isaiah 40:3-5 directly about John, providing the fullest citation of the prophecy John references.

In Matthew 11:10, Jesus identifies John as the messenger who prepares the way, reinforcing the same role John claims for himself here.

Luke 7:27 quotes Malachi about the messenger sent before the Lord, identifying John similarly as the forerunner prophesied.

Luke 1:16 describes John turning many to the Lord, fulfilling the preparatory role hinted at by the wilderness voice.