1. The prophetic allusion and the kingdom
18 He said therefore, “What is the kingdom of God like? And to what shall I compare it? . . . 20 And again he said, “To what shall I compare the kingdom of God?” Luke 13:18; 20 (ESV)

18 To whom then will you liken God, or what likeness compare with him? Isaiah 40:18 (ESV)

2. The outward (extensive) growth of the kingdom
19 It is like a grain of mustard seed that a man took and sowed in his garden, and it grew and became a tree, and the birds of the air made nests in its branches.” Luke 13:19 (ESV)

3. The inward (intensive) growth and the kingdom
21 It is like leaven that a woman took and hid in three measures of flour, until it was all leavened.”
Luke 13:21 (ESV)

4. The principles of the kingdom (Philip Ryken)
a.       The starting point is from a small and seemingly insignificant beginning
b.      Yet from that small and seemingly insignificant beginning, the kingdom of God grows.
c.       From a small and seemingly insignificant beginning, the kingdom of God grows—at times invisibly and almost imperceptibly.

24 Truly, truly, I say to you, unless a grain of wheat falls into the earth and dies, it remains alone; but if it dies, it bears much fruit. John 12:24 (ESV)

d.      This is a fourth principle of its growth: the kingdom of God continues to grow until it reaches all nations.

22 Thus says the Lord God: “I myself will take a sprig from the lofty top of the cedar and will set it out. I will break off from the topmost of its young twigs a tender one, and I myself will plant it on a high and lofty mountain. 23 On the mountain height of Israel will I plant it, that it may bear branches and produce fruit and become a noble cedar. And under it will dwell every kind of bird; in the shade of its branches birds of every sort will nest. Ezekiel 17:22–23 (ESV)

8 But you will receive power when the Holy Spirit has come upon you, and you will be my witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth.”
Acts 1:8 (ESV)

e.       This is the last principle of growth taught in these two parables: From a small and seemingly insignificant beginning, the kingdom of God grows—at times invisibly and almost imperceptibly—until it reaches all nations with its transforming power.

17 Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come. 2 Corinthians 5:17 (ESV)

6 And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ. Philippians 1:6 (ESV)