Book of Mark – The Parable of Mustard Seed

And he said, “With what can we compare the kingdom of God, or what parable shall we use for it? It is like a grain of mustard seed, which, when sown on the ground, is the smallest of all the seeds on earth, yet when it is sown it grows up and becomes larger than all the garden plants and puts out large branches, so that the birds of the air can make nests in its shade.”
With many such parables he spoke the word to them, as they were able to hear it. He did not speak to them without a parable, but privately to his own disciples he explained everything.

Mark 4:30-34 ESV

This parable explains about the kingly rule of Jesus through his current ministry, it seems small and insignificant, some people have heard about it, some people have seen him, but only few responded to follow Him. One day the kingdom of God will be seen as the greatest kingdom of all, when all things will be revealed :)
Even now, we can see how Jesus’ ministry has grown, from 12 disciples, to the believers in all the nations across the earth, however everything will be revealed even more when Jesus come back :)

Book of Mark – The Parable of Growing Seed

And he said, “The kingdom of God is as if a man should scatter seed on the ground. He sleeps and rises night and day, and the seed sprouts and grows; he knows not how. The earth produces by itself, first the blade, then the ear, then the full grain in the ear. But when the grain is ripe, at once he puts in the sickle, because the harvest has come.”

Mark 4:26-29

Book of Mark – The Lamp Under a Basket

And he said to them, “Is a lamp brought in to be put under a basket, or under a bed, and not on a stand? For nothing is hidden except to be made manifest; nor is anything secret except to come to light. If anyone has ears to hear, let him hear.” And he said to them, “Pay attention to what you hear: with the measure you use, it will be measured to you, and still more will be added to you. For to the one who has, more will be given, and from the one who has not, even what he has will be taken away.”

Mark 4:21-25 ESV

Book of Mark – Parable of the Sower

…and in his teaching he said to them: “Listen! Behold, a sower went out to sow. And as he sowed, some seed fell along the path, and the birds came and devoured it. Other seed fell on rocky ground, where it did not have much soil, and immediately it sprang up, since it had no depth of soil. And when the sun rose, it was scorched, and since it had no root, it withered away. Other seed fell among thorns, and the thorns grew up and choked it, and it yielded no grain. And other seeds fell into good soil and produced grain, growing up and increasing and yielding thirtyfold and sixtyfold and a hundredfold.” And he said, “He who has ears to hear, let him hear.”

Mark 4:2b-9 ESV

Book of Mark – The True Family

And his mother and his brothers came, and standing outside they sent to him and called him. And a crowd was sitting around him, and they said to him, “Your mother and your brothers are outside, seeking you.” And he answered them, “Who are my mother and my brothers?” And looking about at those who sat around him, he said, “Here are my mother and my brothers! For whoever does the will of God, he is my brother and sister and mother.”

Mark 3: 31-35 ESV

Again and again we can see a pattern in the people around Jesus at that time. There are 2 groups of people, one group is the one who understand or believe in Jesus and they’re inside trying to get close to Jesus. While the other group is the one who do not understand or do not believe in Jesus, they’re always outside this group. In this part of the passage, ironically it’s Jesus’ family who’re outside, they’re not part of the people who sits around Jesus to hear what he’s teaching about.

On top of that we can see from the previous passage that Jesus family (Mary and Jesus’ brothers) didn’t think that Jesus is sane. Therefore it’s obvious that they’re not really here to come and listen to Jesus’ teaching, instead they’re coming to seize him. In contrast the people inside Jesus’s inner circle, are the one who believes and trust in His teaching and willing to do the will of God. That’s why what Jesus said made sense, Jesus’ true family are the people who does the will of God!