Some scholars have argued that entos hymōn can mean "within your grasp" or "within your reach." Even "near to hand."
That translation tips the meaning slightly. Instead of a spatial commentary, the kingdom of God being inside or outside, a translation of "within your reach" is a prompt to action. The kingdom is close, but it is something that has to be realized. The kingdom of God is within your reach, so reach out and grasp it. The kingdom is right in front of you, so seize it.
My favorite parables of the kingdom that echo this sentiment are the parables of the Treasure in the Field and the Pearl of Great Price. The kingdom is close and available--a valuable pearl or a buried treasure--but you have to act energetically and decisively to secure it. Something extraordinarily valuable is "within your grasp." Will you act decisively to seize it? The kingdom of God, Jesus is saying, is like that.
Trouble is, these parables are from Matthew and not Luke. So we're on shaky ground using these examples to unpack what Luke might mean in 17.21. Still, we do see this theme in Luke. Consider:
“So I say to you, ask, and it will be given to you. Seek, and you will find. Knock, and the door will be opened to you. For everyone who asks receives, and the one who seeks finds, and to the one who knocks, the door will be opened." (Luke 11.9-10)
