The kingdom of God, therefore, as consisting of those who acknowledge, worship, love, and obey Jehovah as the only living and true God, has existed in our world ever since the fall of Adam. It has ever been the light and life of the world. It is the salt by which it is preserved. It is the leaven by which it is ultimately to be pervaded. To gather his people into this kingdom, and to carry it on to its consummation, is the end of all God’s dispensations, and the purpose for which his eternal Son assumed our nature. He was born to be a king. To this end He lived and died and rose again, that He might be Lord of all those given to Him by the Father.

Charles Hodge, Systematic Theology, Vol. 2, 597.