Albert Barnes Commentary Luke 17:21

"neither shall they say, Lo, here! or, There! for lo, the kingdom of God is within you." — Luke 17:21 (ASV)

Lo here! or, Lo there! When an earthly prince visits different parts of his territories, he does it with pomp. His movements attract observation, and become the common topic of conversation. The inquiry is, Where is he? which way will he go? and it is a matter of important news to be able to say where he is. Jesus says that the Messiah would not come in that manner. It would not be with such pomp and public attention. It would be silent, obscure, and attracting comparatively little notice. Or the passage may have reference to the custom of the pretended Messiahs, who appeared in this manner. They said that in this place or in that, in this mountain or that desert, they would show signs that would convince the people that they were the Messiah .

Is within you. This is capable of two interpretations:

1. The reign of God is in the heart. It does not come with pomp and splendour, like the reign of temporal kings, merely to control the external actions and strike the senses of men with awe, but it reigns in the heart by the law of God; it sets up its dominion over the passions, and brings every thought into captivity to the obedience of Christ.
2. It may mean the new dispensation is even now among YOU. The Messiah has come. John has ushered in the kingdom of God, and you are not to expect the appearance of the Messiah with great pomp and splendour, for he is now among you.

Most critics at present incline to this latter interpretation. The ancient versions chiefly follow the former.