This is a question people have been asking for centuries, starting with the apostles. One of the problems we have with this question is that our minds immediately think in terms of earthly kingdoms with geographic locations headed by someone who is a king. The other problem is that people sometimes mix the subjects of the coming of the kingdom of God and the second coming of Jesus.
The Pharisees asked Jesus when the kingdom of God would come, and he gave a surprising answer. “The kingdom of God does not come with your careful observation, nor will people say, ‘Here it is,’ or ‘There it is,’ because the kingdom of God is within you.” (Luke 17: 20-21) In other words, we won’t be able to physically observe a kingdom as a location with geographic boundaries, because the kingdom that Jesus is talking about is within us. Its geography is our heart, our soul – our inner being.
Jesus gives added understanding of this verse in the Gospel of John when he says, “If anyone loves me, he will obey my teaching. My Father will love him, and we will come to him and make our home with him.” (John 14:10) If we love God and obey his teaching, God and Jesus will take up residence in us. By the power of the Holy Spirit, God draws us closer to him each day. We desire to be in his presence, we seek to know him more through prayer and scripture, and to participate in the sacraments if we a part of a sacramental church.
The fruit of the Spirit becomes evident in our lives. Love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control are the visible signs that the kingdom has come. (Galatians 5:22-23) When we love the people in our lives, showing patience, kindness and gentleness; when we are faithful to God, showing goodness and self-control, the Kingdom of God is in us.
Might not this be the kingdom Jesus is talking about when he instructed the disciples how to pray? “Thy kingdom come, thy will be done, on earth as it is in heaven.” In the Lord’s Prayer, we pray for the coming of God’s kingdom in us and that his will be accomplished through us.
As earthly kingdoms experience the rise of enemies with whom they have to do battle, so also does God’s kingdom in us have to do battle with God’s enemy, the devil. He constantly strives to lure us away from God’s kingdom into his kingdom. But God equips us for this spiritual battle with his word, the Holy Spirit and the supporting allies of other kingdoms residing in our brothers and sisters in Christ and the Church.
When will the Kingdom of God come? When we love Jesus, obey his teaching and invite the Father and Jesus to make their home in us.