The kingdom matters because God’s anointed (Christ) has been raised up with all authority in the earthly and heavenly realms. In him, God’s reign has returned to earth. That’s the gospel.
The kingdom matters because God’s good news calls everyone to recognize his Christ as our Lord. Our heavenly sovereign’s kindness (grace) calls us from reliance on every other form of power (repentance), raising us to life in his Son (regeneration) as we trust his leadership (faith). That’s our response to God’s gospel.
The kingdom matters because the gospel re-establishes us as the people of God in Christ, the kingdom that comes to life in the king. His Spirit empowers us to serve as agents of his government on earth. We honour the king (worship) by embodying his wise governance (love) in making peace (forgiveness, reconciliation). He invites us to present matters that need his attention before his throne (prayer) as we serve as the corporate expression of the king (church) in his realm.
The kingdom matters because this is what God is doing on earth. With his kingdom, God saves us from a self-oriented life of “looking after number one,” reconstructing life on earth around a new Number One. We discover our life as servants of the king.
The kingdom matters because it’s the only thing that lasts. In Christ’s kingdom wars cease, justice returns, forgiveness reigns, love endures. Only the reign of the resurrected king will persist through all ages.
The kingdom matters because it’s God’s gift to all who trust him: Fear not, little flock, for it is your Father’s good pleasure to give you the kingdom (Luke 12:32).
So how do we live in his kingdom?
Seriously, don’t listen to preachers who tell you it’s a free gift to add to your existing life, or a means of finding your best self. Selfish marketing techniques are incongruent with God’s gospel.
According to Jesus, citizenship in God’s kingdom involves a heart transplant in what we treasure:
Luke 12:32–34 (ESV)
32 Fear not, little flock, for it is your Father’s good pleasure to give you the kingdom. 33 Sell your possessions, and give to the needy. … 34 For where your treasure is, there will your heart be also.