Then he quotes Isaiah 40: ‘The voice of him that crieth in the wilderness, Prepare ye the way of the LORD, make straight in the desert a highway for our God’ (Isaiah 40:3). John says that he is that voice, predicted by Isaiah as the forerunner.
God will not deal with us if we do not show we are serious about finding him. We must make straight his paths. The people of John’s day understood what this figure meant. Our sins stand in the way of the Lord. If we wish him to come to us, we do not put obstacles in his way, but we clear the ground making it as easy as possible for him to come.
This is double prophecy, dual sense in prophecy. There are people today who say, there's no dual sense in prophecy. The Scripture and prophecy only have one meaning. No, the Scriptures are full of dual sense in prophecy. It’s simple; this is how it works. The first fulfilment of the prophecy of Isaiah in chapter 40 was the release of the Jews from captivity in Babylon. The prophecies are literally fulfilled, when the captive nation is released, and a vast number, a large number – a minority altogether – are able to return to Jerusalem and to Israel. But that's only a partial fulfilment. That in its turn – that token, that literal token – is a prediction of the coming of Christ, and how multitudes of Jews and Gentiles, like captives released, will return to God through Christ. This is how Mark applies it. It has already been applied by the Jews to the release from the Babylonian captivity, and now for the second time it's applied by Matthew, Mark, and Luke to the coming of John the Baptist, and the coming of Christ. The prophecy had two fulfilments: a physical fulfilment which only partly honoured the terms of the prophecy, and a spiritual fulfilment in the coming of Christ. That is how prophecy works, and you don't understand Isaiah unless you understand the dual sense in prophecy. A token fulfilment; a true fulfilment, to all the great prophecies.