The kingdom of heaven is like treasure hidden in a field, which a man found and covered up. Then in his joy he goes and sells all that he has and buys that field.
John Piper, in a sermon, “The Kingdom of Heaven Is a Treasure”, helps us see the main point in Matthew 13:44
You don’t buy it. You get it freely because you want it more than you want anything else. It’s as if a poor child entered a toy store and the owner said: you can have the best and most expensive toy in this store if you want it more than anything else. In other words, there is a condition for having the kingdom—for having the King on your side and as your friend—but the condition is not wealth or power or intelligence or eminence. The condition is that you prize the kingdom more than you prize anything else. The point of selling everything in this parable is simply to show where your heart is. “Where your treasure is, there your heart will be also” (Matthew 6:21). And if your heart is to have the kingdom above all things, then Luke 12:32 comes true for you: “It is your Father’s good pleasure to give you the kingdom.” To give you the kingdom!
So the point of Matthew 13:44 is that the kingdom of God is so valuable that losing everything on earth, but getting the kingdom, is a happy trade-off. Or to be more personal and specific, we can lose everything with joy if we gain Christ. Don’t miss the word “joy” in this verse: “In his joy he goes and sells all that he has and buys that field.” The loss of all things is not sad if we gain Christ.