Whoever does the will of my Father in heaven will enter the Kingdom of God. Entrance into (belonging in) the kingdom of God is both the basis and raison d’etre for discipleship. The kingdom of God, as preached by Jesus, is nothing other than a world governed by peace, justice, and the conservation of creation. If the kingdom was the central message of Jesus Christ, the task of the disciple is therefore that of building a world where peace, justice and respect for creation are the dominant values (cf. Pope Benedict XVI, Jesus of Nazareth). When Jesus, therefore, predicates the kingdom of God to doing God’s will, he is essentially saying that God’s will and the establishment of the kingdom is basically one and the same thing. For the will of God is that peace and justice reign (cf. I Timothy 2:4). 
Even though the in-breaking of the kingdom has already taken place (in the birth and ministry of Jesus Christ), it still remains the goal of the creative process that has to be attained. This is why we still pray for the coming of the kingdom in the Lord’s Prayer. For when we pray for it, we ask God to bring to fullness the already present world (of justice and peace) that we endeavor to build. This is the kingdom to which we all look forward, the coming of which we anticipate during this Advent season.