Why did Jesus speak in parables? What was their purpose?
The word parable means to “cast alongside” something else, so Jesus used parables in His teachings in this manner. He would cast out a truth alongside an earthly story. Sometimes their purpose was to hide the meaning; sometimes it was to make it plain, but Jesus used parables as an earthly story about a heavenly concept. He was trying to explain the Kingdom of God, so He used physical examples that the people would be familiar with. This was His way of illustrating profound spiritual truths, and they were often tied to the Word of God, but His disciples didn’t always understand them, so Jesus needed to explain them, however, in some cases, He choose to hide their meaning.
To Hide the Meaning
When Jesus’ disciples asked Him about His speaking to the crowd in parables, they “said to him, “Why do you speak to them in parables” (Matt 13:10)? A lot of people want to know the answer to that question. Why did Jesus speak to them in parables? Jesus “answered them, “To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given” (Matt 13:11). So why didn’t Jesus let them understand the parables? Maybe they could’ve learned something, however, Jesus told His disciples that, “This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand” (Matt 13:13). Why didn’t they understand? Because you can hear something, but not really listen. How many listen to the same emergency procedures on an aircraft after they’ve heard it a hundred times? Someone who’s never flown before will be listening and hearing, and since they were listening, they’ll know what to do. But the religious Jews didn’t really want to listen, hear, and obey Jesus’ teachings; even though they were from Scripture! They wouldn’t even listen to Him. They were blind in Isaiah’s day (Isaiah 42:18-20), and they were blind still (Matt 23:24). More than that, they didn’t have “ears to hear,” meaning, they didn’t want to hear the truth. Those who know the Father know Jesus, but they knew neither, so they could not understand Jesus’ teachings in the parables. They could not understand because they choose to not understand.
To Reveal the Meaning
Even though Jesus hid the meaning from the religious crowd, He let the disciples know their meanings. Sometimes, they had a little trouble grasping them, so Jesus had to make it clear about some of the parables. The beginning point of understanding Jesus’ parables is hearing His Words. He says, “He who has ears to hear, let him hear” (Luke 8:8b), but it’s a lot more than hearing. Jesus said that “everyone then who hears these words of mine and does them will be like a wise man who built his house on the rock” (Matt 7:24). Everyone might have heard about the fire exits in the theatre, but we all hope they were listening. You can listen without really hearing. You can hear about a fire exit, but knowing exactly which one you need to take in a fire could be a matter of life or death. Ears have to be willing to hear. Then, they have to be eager to do what they have heard. Head knowledge alone is never enough.
Parable about Forgiveness
Jesus gave one of the most beautiful illustrations of forgiveness in Scripture in the Parable of the Unforgiving Servant. In this parable, a man was brought before the king having a debt of “ten thousand talents” (Matt 18:24), an impossible amount for him to pay off. After begging the king for forgiveness, the king grants the man freedom and cancels his enormous debt (Matt 18:26-27). The king represents God, and we are the servant who owes an unpayable debt…a debt so great that we could never pay it off in a million lifetimes. A billion good works couldn’t buy us one second in heaven. The servant had a debt he could never hope to pay…but the king is good…as our God is good. He forgives (1 John 1:9). Tragically, “that same servant went out, he found one of his fellow servants who owed him a hundred denarii, and seizing him, he began to choke him, saying, ‘Pay what you owe’” (Matt 18:28). That servant’s debt of only a hundred denarii is something he could have worked off in a day, so it was a debt that was payable, but the wicked servant refused the other servant’s plea for mercy and “put him in prison until he should pay the debt” (Matt 18: 30), meaning, he could never pay that debt off because he couldn’t work it off in prison! Jesus is telling us that God has forgiven us a debt so large that it is impossible for us to pay, so how can we not forgive others who owe us a debt infinitely lesser than that which we owed God? How can we not forgive others since God has forgiven us so much; past, present, and future? Our debt to God is infinite, but with our fellow man, it is not so. We have no reason not to forgive since we’ve been forgiven so much more…more than we can even imagine. Remember, our forgiveness cost Jesus His suffering, shame, and death on the cross. Our friends could never have that much debt owed to us, nor we to them! Jesus warned that “my heavenly Father will do to every one of you, if you do not forgive your brother from your heart” (Matt 18:35).
Jesus used parables to hide the meaning to the unrepentant…the ones that didn’t have “ears to hear,” but He also used them to make the teachings of God plain to those who would not only listen, but would hear. And, they would not only hear, but they would actually do what Christ commanded (Matt 25:40). Those who do what Jesus taught are doing the will of the Father. The more a person obeys God, the more truth He will reveal. The best way to know the God of the Word is to know the Word of God…and even the Son of God, also is called the Word of God (John 1). He is the truth, the life, and the way (John 14:6). In fact, He is the one and only way to the Father (John 6:44; Acts 4:12). That’s plain for anyone who has “ears to hear” or “eyes to read.”
Here is some related reading for you: 5 Parables of Jesus to Learn From 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible: English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.