Mark 4:30 And he said, Whereunto shall we liken the kingdom of God? or with what comparison shall we compare it?
Jesus continues to speak about the spiritual kingdom of God, now he uses a parable as a comparison.
Mark 4:31 It is like a grain of mustard seed, which, when it is sown in the earth, is less than all the seeds that be in the earth:
The tiniest seed sown in a heart, a little of God's word sown with faith:
Mark 4:32 But when it is sown, it groweth up, and becometh greater than all herbs, and shooteth out great branches; so that the fowls of the air may lodge under the shadow of it.
This could be a parable of the church, all who profess to be Christians. The word in hearts has unusual growth; from a tiny start a great church grows. Suppose the seed was misunderstood? There would be error in the church, birds in the branches. The fowls of the air represent satan and his powers. In all who profess Christ, some are among us who are not of us. They come to take away the word.
Gal 1:6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
Gal 1:7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
Gal 1:8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
Gal 1:9 As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.
Mark 4:33 And with many such parables spake he the word unto them, as they were able to hear it.
Parables illustrate a message on two levels. The spiritual hearer should see spiritual things, the natural man just hears a story.
Mark 4:34 But without a parable spake he not unto them: and when they were alone, he expounded all things to his disciples.
Jesus always used parables when he spoke, later he would explain them to his closest disciples. Some people will not receive God's good message. There is a parable for them:
Mat 7:6 Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you.
The word falling on good ground will take root. If they will not receive the pure word, but abuse it and you, then speak to these in a parable, and move on. Remember, speak words of grace in love, do not give back angry words. They will see God in you.
1 Pet 2:12 Having your conversation honest among the Gentiles: that, whereas they speak against you as evildoers, they may by your good works, which they shall behold, glorify God in the day of visitation.