As in Matthew and John, Mark tells us that the arrest of John the Baptist is the signal for the beginning of Jesus' public ministry. He has been active before that, as a kind of disciple of John (or so it would seem looking on from the outside), but once he hears of John's arrest things change quickly and radically: he withdraws from Judea into Galilee, and his own work of preaching, healing, and exorcism gets under way.
There is a strong contrast in Mark's gospel between the preaching of the Baptist and the preaching of Jesus. John preached a baptism of repentance for the forgiveness of sins. Jesus preaches the gospel of God, the fulfillment of time, and the imminence of the kingdom of God. It is time to repent and to believe in the gospel.
What has come between the preaching of John and the preaching of Jesus is Jesus' baptism and his temptation in the wilderness, both described briefly but profoundly by Mark. The opening of the heavens at the baptism is the answer to an ancient prayer of Israel that God would open the heavens, intervene, visit his people, come down, save them. Mark tells us that this prayer of Israel is answered in the moment of Jesus' baptism: the Spirit comes from the opened heavens to anoint Jesus while the Father's words, accompanying the Spirit's anointing, recognise him as the beloved Son with whom the Father is well pleased.
Jesus is now established in his identity. It happens at the level of his divine nature (if we can put it like this) in his baptism. And it happens at the level of his human nature in his temptation in the desert. There, as Mark describes it, the Son of God (Mk 1:1), is the centre of creation, tempted by the devil as Adam and Eve were, he is with the wild beasts as the prophecies foretold concerning the child who would lead the people into the kingdom, and the angels ministered to him as was promised for God's chosen one in the psalms.
Hence the huge difference between the preaching of the Baptist - a call to repentance and to a symbolic enactment of it in baptism - and the preaching of Jesus - carrying the gospel of God, announcing that the time is fulfilled, saying that the kingdom of God is at hand. There is a whole new rationale for repentance, a whole new level of spiritual life, not just to try to tidy ourselves up and sort ourselves out, but to 'believe', to open ourselves to the approach of God, to be ready, like the first disciples, to answer his call and if necessary to leave everything we have known up to now in order to follow him into his kingdom.
We see this transforming work of the Spirit accompanying the preaching of Jonah as it accompanied the preaching of the Baptist and then of Jesus. Jonah's attempts to avoid the mission to which he was called are finally frustrated and, still complaining, he takes on the seemingly impossible task of calling a huge city to repentance. But just one day into the work he finds that everybody repents, including God who, we are told, 'repents of the evil he had threatened to do to them'. We can imagine Jonah, and John the Baptist, both saying 'we are unworthy servants, we have only done what was our duty'. In other words they allowed themselves, and their lives, to be instruments of God's purpose for others. The same with Peter and Andrew, James and John: they too allow the Spirit to work powerfully in them so that they can leave everything in order to follow Jesus.
'The world in its present form is passing away': so Saint Paul in today's second reading. This transformation comes about through the work of Jesus who enters into the first creation in order to establish within it the seeds of the new creation. It is already intimated in the lives of Jonah and John the Baptist. It will happen decisively in the lives of the Apostles. In all cases the pattern is same: the Father speaks, the Spirit anoints, and the Word becomes flesh in the lives of all who hear and receive this anointing. Everybody who has been baptised is called to this - to see everything in a new light, to experience a new freedom, to contribute to the work of building the civilization of love. We live in the time of fulfillment and we are called to build the kingdom in whatever ways are available to us.