Matthew 13:44-46
44 Again, the kingdom of heaven is like unto treasure hid in a field; the which when a man hath found, he hideth, and for joy thereof goeth and selleth all that he hath, and buyeth that field.
45 Again, the kingdom of heaven is like unto a merchant man, seeking goodly pearls:
46 Who, when he had found one pearl of great price, went and sold all that he had, and bought it.
The Grace New Testament Commentary - Mathew 13:44-46
13:44 In this parable "a man" (i.e., Christ) finds a "treasure (i.e., the kingdom, or believers) hidden in a field (i.e., the world)." He enthusiastically "sells all that he has and buys that field." The problem this parable addresses is the value of the citizens of "the kingdom" to Christ. The parable explains that they are of supreme value. Jesus is the one who gave all He had for the buried treasure in the field. He gave His life for His own (1 Pet 1:18-19). His sacrifice shows how precious to Christ are "the kingdom" subjects (1 Cor 6:20: 2 Cor 8:9).
In the Parable of the Hidden Treasure, some incorrectly identify the treasure as eternal life. In this view the man who sells all is seen as a seeking sinner buying his own eternal life by committing his life to Christ in radical, obedient discipleship. The problem with this interpretation is that the Bible consistently teaches that a person is born again, not by his sacrifice but by the Lord's. No one must think he can pay any part of the redemption price himself.
13:45-46 The first two parables are parallel in that they involve sowing. The second two parables are parallel in that both describe the development of the kingdom. The Parables of the Hidden Treasure and of the "pearl of great price" are also parallel. Both involve the purchase of something valuable. Thus it would be natural in context to interpret the pearl hunter and man seeking to buy a field as the same individual and the objects purchased as having a similar or identical identification.
What is the value of the citizens of the kingdom to Christ? They are of supreme value. Just as the businessman gave "all that he had" for a valuable pearl, so Jesus gave all He had (His life) for His own. In Jesus' case He purchased them not for what they were but for what they would become through His grace.
Charles Bing - Grace, Salvation, and Discipleship - Parables of the Hidden Treasure and Pearl of Great Price, Matthew 13:44-46
(Salvation) Interpretation: These two parables teach that to enter the kingdom of God a person must give up everything and pay a great price.
(Discipleship) Interpretation: These two parables teach that a mystery of the kingdom is that it will include both of God's treasured people, Israel and the Gentiles, whom He bought at a great price.
The first interpretation sees the parables as teaching about the great worth of the kingdom and the high cost of entering it - an evangelistic purpose. However, the context does not support this view. The purpose of these parables is to hide truth from unbelievers and reveal truth to believers (Matt. 13:10-17; Mark 4:10-12; Luke 8:9-10). It is to teach "the mysteries of the kingdom of heaven," that is, a new truth about the kingdom of God. Jesus is teaching about the nature of the kingdom that reveals something new about it. If He is only teaching about how to enter the kingdom by paying the price of discipleship, this teaching is nothing new to the disciples because Jesus previously spoke of the conditions of discipleship (Matt 10:32-33; 37-39; 11:28-30). Besides, God does not hide the truth of the gospel from unbelievers.
The new "mystery" teaching is that those who are Jews and those who are Gentiles will be together in the kingdom. In the first parable, the treasure in a field represents Israel in the world. They are hidden for a time because they are dispersed among the nations, but will be re-gathered and restored by the One who paid a great price for them (1 Corinthians 6:20, 7:23) - Jesus Christ. In the second parable, the precious pearl speaks of the church that is never hidden, but is also purchased by the highest price - the death of Jesus Christ.
Jesus came to "seek and to save that which was lost" (Luke 19:10). He purchased Israel and the church through His death on the cross. An unbeliever has nothing of value to God by which he can purchase the kingdom of God (By the way, in the first parable, not just the treasure is purchased, but also the field, which would have to be explained if this is (Salvation)).
(The Discipleship view) teaches something precious that has not been previously revealed, but which believers need to know. God's people, Israel, and God's people, the church, will be together in the kingdom. God so values both groups that He paid the highest price for them - His own Son. As Christians, we can marvel at God's sovereignty, wisdom, and grace that redeems Israel and also raises up the church from among the Gentiles to be together in one kingdom.