The first verse that many use to try to perpetuate the idea of a spiritualized Kingdom is Luke 17:20-21[And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation: Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you. ]. Many people, such as amillennialists, point to this translation of the Greek word “entos” which has been translated by the KJV as “within you”. They say that the Kingdom of God is only spiritual or is somehow mystically inside a person. However, in this passage, to whom is Jesus speaking? Jesus is responding to the Pharisees, not His disciples! Jesus is answering the Pharisees’ question, “When the Kingdom of God should come?” In the next verse, verse 22, it begins, “And he said unto the disciples”. In the same context, he turns and addresses his own disciples in verse 22. The Pharisees were not his disciples! In verses 20 and 21, he’s talking to the Pharisees, and then he turns to talk to his disciples.
The Pharisees rejected the signs that Jesus had given to prove that he was the Christ; the Messiah. How could God's spiritual kingdom be within them? If the kingdom of God were within anyone spiritually, would it have been within the unbelieving Pharisees?
This verse completely goes against the view that the kingdom of God is within the hearts of people that have accepted Jesus as the Messiah, because the only time in the Scriptures that it is used, it is used in reference to those who had rejected Jesus to be the Christ.
The English translation “within you” does not make any sense because the Pharisees had rejected Jesus as their Messiah. The 1611 KJV translators were not sure how best to translate this word, so they included a marginal note with the alternate reading, “among you”. This is obviously the true meaning of the word in this context. It is translated “among you” or “in your midst” in various other translations such as the NASB, RSV, BBE, NLT, NJB, NET and the Rotherham translation.