These two parables are somewhat similar. There is a man and a treasure, and after he finds it, he goes and sells everything he has and buys the treasure. These two parables are universally thought to be positive parables, unlike the first four.
We have already interpreted two of the symbols found in verse 44—"the field" and "the man." We find in verse 37 that the one who sows good seed is "the son of man." Wherever the term "man" shows up in these parables, it tends to mean "Christ." The "Son of Man" is obviously Christ, and "man" in these two parables is also Christ. In verse 38, Jesus says the field is "the world." In these parables, "treasure" is found in the world, and a "man," Christ, is doing something with it.
How is "treasure" used in Scripture? Obviously, the literal meaning of "treasure" is what first comes to mind: Jewels, gold, silver, other precious metals, art, and fine clothing would be considered "treasure." But this is a parable, and a parable is metaphorical. The symbol must mean something other than just a jewel, a chest full of coins, or a collection of fine art. How is "treasure" used metaphorically in the Bible?
In Exodus 19:5, God says that if Israel "will indeed obey My voice and keep My covenant, then you shall be a special treasure to Me above all people." Psalm 135:4 says, "The LORD has chosen Jacob for Himself, Israel for His special treasure." Notice also Malachi 3:16-17:
Then those who feared the LORD spoke to one another, and the LORD listened and heard them; so a book of remembrance was written before Him for those who fear the LORD and who meditate on His name. "They shall be Mine," says the LORD of hosts, "on the day that I make them My jewels."
The margin on "My jewels" is literally "special treasure."
We see the same thing in the New Testament. I Peter 2:9-10 says:
But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy.
Notice the progression of identity here. First, this "special treasure" was Israel, the one God made a covenant with on Mount Sinai. In the Psalms, He calls His "special treasure" specifically "Israel" and "Jacob." In Malachi, God describes His "special treasure" as "those who fear His name" and "those who speak one to another" about His way. In I Peter 2 it is the elect are His "special people." It has gone from "Israel," to a little bit more general—"those who fear His name"—to specific again—"His special people, a holy nation."
In Matthew 13, the "treasure" is the church, which fits all of these descriptions. It is spiritual Israel, "the Israel of God" (Galatians 6:16). The church is composed of those among all the people of the earth who truly fear His name. And because God called us out of the world separately and individually, the church is now a people who were not a people.