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. Luke 17:20, 21.
(TDG 186.1)
The kingdom of heaven can be felt, but not seen. The inward working of the Spirit of God is compared to leaven.... Christ by this parable illustrates the human heart. The leaven of truth, working inwardly will be revealed in the life. The heart must be cleansed from all impurity, man must be fitted with traits of character that will enable him to do service for God in any line. The process is invisible by which the leaven changes the mass of meal into which it has been introduced, but it works until the meal is converted into bread. So must the Spirit of God work a radical change. New faculties are not supplied, but a thorough change is made in the employment of those faculties. The natural inclinations are softened and subdued. New thoughts, new feelings, new motives are implanted. But while every faculty is regenerated, man does not lose his identity....
(TDG 186.2)
The Scriptures are the great agency in this transformation. Christ prayed, “Sanctify them through thy truth: thy word is truth” (John 17:17). In this great work we are laborers together with God. With the divine agency there is to be the cooperation of the human instrument....
(TDG 186.3)
The meal in which the leaven has been hid represents the heart that believes and receives Jesus. Christ works out the principles which He alone can work in. The world looks upon this class as a mystery which they cannot solve. The selfish, money-loving man lives to eat and drink and enjoy his worldly goods. But he does not keep eternity in view. He loses the eternal world from his reckoning. But those who receive and believe the truth have that faith which works by love and purifies the soul from everything sensual. The world cannot know them, for they are keeping in view eternal realities. A motive power is working within to transform the character. A constraining influence received from heaven is working like the leaven hid in the meal. The love of Jesus has come into the heart with its redeeming power to conquer the entire being, soul, body, and spirit.—Manuscript 82, June 26, 1898, “The Leaven of Truth.”
(TDG 186.4)