The ancient kingdoms of Herods and Caesars were nothing at all like a mustard seed, or a pearl, or a slave who invested a few coins successfully. The kingdoms of the Selucids and the Ptolemys were nothing at all like a sower wildly scattering seeds, or a landowner who paid latecomers a day's wage, or a woman baking with yeast. Rather, the kingdoms of ancient overlords were like huge stretches of territory inhabited by supposedly free people who paid exorbitant taxes while living in annual fear from the very real threat of invasion by conquering armies. The kingdoms of earth were like an army on the march, like a mining colony of slaves, like a large scale construction project that required everyone in town to work two jobs for a number of years - and made them pay for the privlege!
The kings of the ancient world were overlords who seized things from people against whom they remained always aloof. They were domineering autocrats who could casually execute any one of their subjects, sometimes literally on a whim. The kings of the earth were nothing at all like a father embracing and forgiving his truly despicable offspring. They were nothing at all like a wealthy host who invited vagrants and beggars to an expensive party when his friends didn't show up. They were nothing at all like a small child who obediently came when called, and then sat there silently, serving as an ironic illustration of "greatness".
The word "kingdom" for Jesus was a set up, a word game, a mysterious twist. According to Jesus, God's kingdom was going to be full of children and people with one eye, full of poor people and only a very few rich guys, and possibly even scribes who were focused enough to suggest actually loving God and actually loving their neighbor. For Jesus, the kingdom was like a large banquet table that welcomed everyone but reversed all their ideas about who was important.
For Jesus, God's kingdom was not "coming soon". It was already "near". Yet, Jesus prayed that it might "come". It was not visibly in the midst of them. It was only "at hand". It was always being proclaimed, and yet only "some" would "see" it. Jesus told one man he was "not far" from the kingdom, and he told his disciples to announce it had "come near" to individual towns. He said his kingdom was not divided, and it was not of Satan, and it was not like those kingdoms Satan offered to give him. The kingdom was said to be like things that individuals could possess, move, and hide in secret places, and yet Jesus also said God would give it (collectively) to his "little flock". And having already prayed it would come near, and having said that it was near, and having said it was not far from some, and had come near to others, Jesus came to Jerusalem and predicted a volatile future and said "when you see these things happen, you will know the kingdom is near". It was near. It had come near. It was coming near. It would be near in the future.
That is one very strange kingdom.
In the fourth Gospel, Jesus stands before Pilate of Rome and makes all of this blatant. "My kingdom is not of this world." That line is not in the synoptic literature, but it still seems like the only conclusion that a reader should draw. Whatever Jesus meant by the term "kingdom", it was nothing like earthly kingdoms. Whatever Mark, Matthew, and Luke intended their audiences to understand by this term, there is no cause for scholars to excerpt *some* of those writers' dozens of uses while ignoring all of the others, as if being selective about usage in context can support the idea that Jesus intended to build a political kingdom.
When Paul wrote all about "agape" to Corinth, he was redefining the term. No Greek person had ever used such language to denote what 1.Cor.13 is suggesting. The highest form of "love" in pre-Christian Greek was the term "philia". ((Check the listings in Liddell-Scott some time. The instances and variants of that root vastly dominate those of "agape". It's not even close.)) So, in the same way, in the Gospels, Jesus is making an effort to systematically redefine how this word could be used.
In the Gospels, then, what demonstrative clues offer a hermeneutical recourse for understanding Jesus' use of the term "kingdom"?
Let's go back to Jesus' Moral Biography.
In Jesus' private life long before public ministry, his motivation (according to Matthew, implicitly) was to please God. He wanted to obey God, not just by obeying the Hebrew commandments, but by keeping a high standard in his conscience. Everything Jesus talked about paints the picture of someone who cared deeply and personally about pleasing God, doing what God liked, living the kind of life that would make God "well pleased". According to Matthew 5-7 (implicitly), Jesus wanted to possess God's kingdom, and he expected to receive it. He longed to see others live righteously before God. He lived his life focused on God at the expense of public approval and earthly rewards. Jesus gave up his own property and forgave those who wronged him. He loved his enemies because he cared most about "filling up" God's commandments. He went above and beyond in these efforts. He contented himself with little physical comfort and he despised money. He honored God devoutly, but privately. He gave money in secret. He prayed secretly. He snuck away to pray like he was every day re-burying his own pearl of great price. But most of all - Matthew says "first" of all - Jesus sought after God's kingdom and God's righteousness.
Jesus sought first God's kingdom. He obeyed God as his personal King. He desired most of all that God's name would be hallowed, and that God's kingdom would "come" (advance? grow? assert itself more often?).
Jesus said no one would enter the kingdom without having an excessive level of righteousness. He said those who enter the kingdom are those who do the will of his Father in heaven.
This is how the synoptic writers (most obviously Matthew) portrayed Jesus' idea of the kingdom. Whatever may or may not transfer - according to your own judgment - from that literary portrayal to the actual Jesus of History, or however much that portrayal may or may not be accurate, I cannot see any way to avoid one very simple conclusion at a primary level of interpretation. There is only one option I see for understanding Jesus' ideas about "kingdom" in the Gospels. There is only one way to explain it. There is only one way to define it. There is only one way to re-read it. There is only one way. There is only one...
Question: What would I myself personally be putting at risk if I actually pray what he said?
Thy kingdom come...