This is one of those gospels that makes you scratch your head. It seems deceitful to hide the treasure so that you can purchase it from the actual owner of the field. St. John Chrysostom helps us to understand that there is another way to view this, he explains it like this.
The treasure is the gospel (or truth of God), the field is the world, and there really is no owner of that field other than God. So because the world belongs to God, His treasures are gifts to all who come upon them. But they are hidden in order to protect them from the robbers and evil doers of the world, and because they are gifts that require work to find and are hard to obtain. The man once finding the treasure (the gospel of the Lord) learns that nothing else in this world matters, and that once the treasure is found a price must be paid in order to hold onto it. That price is to forgo the goods of this world, and give up everything for it.
The same is true when you encounter the truth of who Jesus is. As C.S. Lewis said, Jesus was either a lunatic, a liar, or the lord. When you study His life and the history books, you will quickly realize that because of the tremendous amount of evidence regarding Jesus’ life, death, and ressurection, the first two can be easily dismissed. Thus we are left with the only remaining conclusion that Jesus was indeed really God. He was incarnated as a man, He lived a perfect life and taught us how God wants us to live. Then died as a sacrifice for our sins, and was ressurected 3 days later. That knowledge puts a claim on your life, you cannot be the same after encountering it. The only rational reactions are to reject it, bury it, and forget about it. Or to accept it, radically change your life, and give up everything to have it. That is what is happening in today’s reading. This man encountered Christ, and was forever changed by it.
It may take some time to gather all of your belongings and give them all up for the treasure, just like sometimes we find the gospel and it takes us time to do anything about it. But when you discover that it is a real treasure, and you realize that nothing else in this world matters, it will cost you everything to hold onto it. But by the time that that comes, you will not care about the loss of the things of this world, because you will have found something far greater, and that will bring you more joy than anything in this world could ever offer. The truth of the lord is truly a treasure, and oh I wish that more would come to realize that, and to learn to value it more than anything else in this world. That is my wish for you, and for all the people of this world.