True Children

 Then they also brought infants to Him that He might touch them; but when the disciples saw it, they rebuked them. But Jesus called them to Him and said, “Let the little children come to Me, and do not forbid them; for of such is the kingdom of God. Assuredly, I say to you, whoever does not receive the kingdom of God as a little child will by no means enter it.”
Luke 18:15–17 

Jesus gives a two-fold rationale command to bring the children to Him: 

First, children are members of the kingdom already. "Of such is the kingdom" means that the kingdom is comprised of such as these children.

Second, everyone in the kingdom of God must receive it as a little child. This applies to children and adults, both. Those who have the first birth must have the second in order to see the kingdom (cf. Jn3:3–8). So, "kingdom" is being used with reference to the visible church in v16, and the invisible/elect/eternal church in v17.

One of the reasons that Jesus insists that children are members of His church, and be brought to Him in all of the privileges of that membership (i.e. the means of grace!), is so that they can learn to receive the kingdom as little children. And one of the reasons that Jesus brings adults into the visible church is so that they can learn to receive the kingdom as little children.

So, dear reader, how have you received the kingdom as a little child? Or, haven't you? God grant unto us all to be true children.

The Longsuffering God of Great Compassion

 Then the Lord said, “Hear what the unjust judge said. And shall God not avenge His own elect who cry out day and night to Him, though He bears long with them? I tell you that He will avenge them speedily.”

Luke 18:6–8

Luke 18:7 implies that, because of His electing love, it is an exercise of divine longsuffering for Him to delay in answering or avenging His people. What a great comfort the greatness of His love should be to those elect. And what a severe warning to those who oppress them.

The Kingdom of God Is Within You

 Now when He was asked by the Pharisees when the kingdom of God would come, He answered them and said, “The kingdom of God does not come with observation; nor will they say, ‘See here!’ or ‘See there!’ For indeed, the kingdom of God is within you.”

Luke 17:20–21

Over the last twenty years, I've often heard the coming of the kingdom in terms of politics and economic—even by those who should have had the Shorter Catechism vocabulary of "Kingdom of Grace" and "Kingdom of Glory" (WSC102). Jesus teaches that the kingdom does not come with observation—and further explains that it cannot be seen because it is within believers. 

Larger Catechism 191 adds "kingdom of His power," referring to His sovereign rule in heaven already, in its thorough, helpful description of what it is: In the second petition (which is, Thy kingdom come), acknowledging ourselves and all mankind to be by nature under the dominion of sin and Satan, we pray, that the kingdom of sin and Satan may be destroyed, the gospel propagated throughout the world, the Jews called, the fullness of the Gentiles brought in; the church furnished with all gospel officers and ordinances, purged from corruption, countenanced and maintained by the civil magistrate; that the ordinances of Christ may be purely dispensed, and made effectual to the converting of those that are yet in their sins, and the confirming, comforting, and building up of those that are already converted: that Christ would rule in our hearts here, and hasten the time of His second coming, and our reigning with him forever: and that He would be pleased so to exercise the kingdom of His power in all the world, as may best conduce to these ends.

One Reason We Need Increased Faith

 “And if he sins against you seven times in a day, and seven times in a day returns to you, saying, ‘I repent,’ you shall forgive him.” And the apostles said to the Lord, “Increase our faith.”
Luke 17:4–5

Forgiving is hard. But the Lord can give us the faith necessary to do it.

Who's Your Master?

 “No servant can serve two masters; for either he will hate the one and love the other, or else he will be loyal to the one and despise the other. You cannot serve God and mammon.” Now the Pharisees, who were lovers of money, also heard all these things, and they derided Him.

Luke 16:13–14

We serve many things, but just one master. It is possible to think that we are serving God, but if He is not Master, then eventually push comes to shove. The Pharisees definitely thought that they were serving God. 

You can have office in the church, be meticulous about your doctrine and behavior, be thought of by others as a very holy man and a spiritual leader—and still, God's omniscient assessment of you may be "lover of money." How grievous that would be, dear reader!

Come, Rejoice with Me

 And when he comes home, he calls together his friends and neighbors, saying to them, "Rejoice with me..."
Luke 15:6

And when she has found it, she calls her friends and neighbors together, saying, "Rejoice with me"
Luke 15:9

It was right that we should make merry and be glad
Luke 15:32

When I was growing up, it was called, "the parable of the prodigal son." From some who understood it a little better, I learned to call it, "the parable of the older brother." But, ultimately, I think it is "the parable of the rejoicing Father." It is an invitation to "come and rejoice with Me," when He saves tax collectors and sinners (cf. Lk 15:1)

Severe Providence and Sovereign Grace

And not many days after, the younger son gathered all together, journeyed to a far country, and there wasted his possessions with prodigal living. But when he had spent all, there arose a severe famine in that land, and he began to be in want. 

Luke 15:13–14

Here is something I don't remember noticing before in the parable of the prodigal son: the severe famine. In the context of the story, a severe famine comes upon the land, in part, to bring this son to an end of himself. How happy this son would be, on account of this famine! Let us be patient under severe providence; it may be an engine that is driven by sovereign grace.

When the Lord Takes Us through Situations That We Can't See Our Way Out of

Now the LORD spoke to Moses, saying: “Speak to the children of Israel, that they turn and camp before Pi Hahiroth, between Migdol and the sea, opposite Baal Zephon; you shall camp before it by the sea. For Pharaoh will say of the children of Israel, ‘They are bewildered by the land; the wilderness has closed them in.’ Then I will harden Pharaoh’s heart, so that he will pursue them; and I will gain honor over Pharaoh and over all his army, that the Egyptians may know that I am the LORD.” And they did so.
Exodus 14:1–4

So the Egyptians pursued them, all the horses and chariots of Pharaoh, his horsemen and his army, and overtook them camping by the sea beside Pi Hahiroth, before Baal Zephon. And when Pharaoh drew near, the children of Israel lifted their eyes, and behold, the Egyptians marched after them. So they were very afraid, and the children of Israel cried out to the LORD. Then they said to Moses, “Because there were no graves in Egypt, have you taken us away to die in the wilderness? Why have you so dealt with us, to bring us up out of Egypt? Is this not the word that we told you in Egypt, saying, ‘Let us alone that we may serve the Egyptians’? For it would have been better for us to serve the Egyptians than that we should die in the wilderness.”
Exodus 14:9–12

The Lord takes His people into situations that they cannot see a way out of, so that He will get glory by delivering us and defeating His enemies. So, dear saint, it we find ourselves in situations that we cannot see our way out of, let us trust Him Who works all things according to the counsel of His saving will (cf. Eph 1:11).