When I pray as Jesus taught, "Your kingdom come," am I asking him to do something he has already done, or for him to complete what he has started?
It is helpful to step back in order to get a larger vista from scripture of some powerful and compelling pictures of the reign of God. Isaiah gives us a picture of a time when dangerous beasts graze with the sheep and play with children (Is 11:1-9). All is peace, safety, and goodness. Daniel shows us a time when the kingdom of God will fill the earth and put an end to the kingdoms of the world with all of its wars and strife (Dn 2:31-45). Several of the prophets give us pictures of health, prosperity, peace, and righteousness (Amos 9:11-15; Mic 4:1-3; Zech 14:9-11)
When Jesus begins his ministry, he begins to preach the "Gospel of the Kingdom" is near with demonstrations of power over the evil forces (Mt 4:17-23), whether demonization, sickness or death (Lk 4:16-43; Jn 11). In fact, he explicitly says that if he is casting out demons by the power of God, then the kingdom has come upon you (Lk 11:20). The Gospel of the Kingdom included justice, mercy, concern for the poor, the widow, and the orphan. Jesus told the crowds that some of them would not taste of death until they see the Kingdom of God come with power (Mk 9:1). The greatest display of power was when Jesus defeated the power of sin (Rom 6:1-7) and death (Rom 6:8-11) at the cross and the tomb, literally shaking the created order (Mt 27:50-53). Ultimately, Jesus was vindicated when he rose from the grave and the kingdom came with power.
The kingdom is not primarily about political, economic, or social realities (Jn 18:36), but about God's rule in his people. This is why Jesus said that the kingdom of God is not here or there, but "within" us (Lk 17:21). However, as his people submit to his reign, there is a transformation of political, economic, and social realities insofar as the hearts of people submit themselves to God's reign in death, burial and resurrection. This is how we act and salt and light (Mt 5:13-16) and participate in the reign of God. Perhaps this is what it means to reign with him in his kingdom (2 Tim 2:12; Rev 20:6; 1 Cor 6:2).
However, the establishing of God's reign is not yet finished; it only began in the ministry of Christ. The kingdom is here (Col 1:13), yet is also still to come (2 Pet 1:11; 1 Cor 15:50; 2 Tim 4:18). Still yet to come is the final consummation when the kingdom will fill the whole earth (Rev 11:15). As Christ was vindicated by his resurrection, so his kingdom people will also be vindicated in their resurrection while the enemies of the kingdom face wrath (1 Thess 1:10). Ultimately even sin and death will be thrown into the lake of fire and all will be glory, peace, safety, and righteousness (Rev 20:14).
At present, we live in between the present age and the age to come. During this time, we should pray for his kingdom in both its future consummation and its present reality. This means being salt and light; and being bearers of God's righteousness, mercy, and goodness. It means teaching and living the Gospel daily as those who are alive from the dead through his resurrection. So, when we pray, "Your kingdom come, your will be done on earth as it is in Heaven," we are in effect praying to God to complete through us what he started. We are praying that God accomplish his redemptive purposes through us as salt and light in the world. This time between the ages is a "second chance" to submit to the righteous, and merciful rule of God, to enter his Kingdom and be ready when the Lord delivers it to the Father (1 Cor 15:24).