John the Baptist is voice of truth and conscience that spoke out in the darkness of the world of his time, declaring the coming of the Lord.
As we await the Savior, we stay awake in hopeful expectation of the Lord's coming by staying focused & devoted to the truth that speaks to us in our hearts, to the whispers of the Holy Spirit in our souls.
Also, we are to be like John the Baptist in another way: proclaiming the Gospel to the world - the gospel that Mark records, as well as the good news that the people of Israel experience when they were delivered from the Babylonian captivity as Isaiah reports in our first reading. Jerusalem was captured in 587, and the people of Israel were either killed in the seige or the battle, or lastly brought back to Babylon as trophies. Isaiah declares to them that this subjection will soon have an end, that they will be restored to the promised land that God had given them.
John's witness was more than just his words, and that is why the Gospel Mark records his way of life well that testifies almost as much as his words. He called the people of his time, and us now, to repentance. We are to do the same, to witness by our lives the Gospel, so that our words are not a resounding gong that is only hollow underneath. St. Peter in the second reading reminds us, just like John the Baptist, of the importance to remain spotless and perfect when the Lord returns. How can we acheive this with our human weakness?
Our season of Advent is of a time of hope, of expectation for the Lord, that is why we share the good news with others. As we await the Lord coming we are to stay awake with hope, as Pope Benedict describes in his encyclical Spe Salvi: "Let us say once again: we need the greater and lesser hopes that keep us going day by day. But these are not enough without the great hope, which must surpass everything else. This great hope can only be God, who encompasses the whole of reality and who can bestow upon us what we, by ourselves, cannot attain. ... God is the foundation of hope: not any god, but the God who has a human face and who has loved us to the end, each one of us and humanity in its entirety. ...His love alone gives us the possibility of soberly persevering day by day...in a world which by its very nature is imperfect. His love is at the same time our guarantee of the existence of what we only vaguely sense and which nevertheless, in our deepest self, we await: a life that is 'truly' life.". [par. 31]
That was the theme of Pope Benedict visit to the United States: Christ our hope.
It's only with our hope in the risen Lord who comes to us Christmas as an infant child, God-with-us, Emmanuel, that we truly hope to find ourselves with God's grace working to be a people full of the spirit and with out blemish.
So this is what we are called to do to prepare the way with hope in the wilderness, the desert of our own hearts and souls. We have to bring down the mountains of our pride, and fill up the valleys of our weaknesses, failures, and fears. If we prepare in this way during Advent, we can trust that our risen Lord whom we make ourselves ready for, will be able to deliver us from our weaknesses, to free us from our slavery to the Babylonian empire of our sins, and restore us to his saving grace.