How should we respond to God’s Kingdom? That is the question being asked and answered in the parable about the hidden treasure and the parable about the great pearl. In both of these parables, Christ describes the great joy that accompanies the finding of a great treasure. The man who finds a treasure that has been buried in a field goes and sells everything that he has so he can buy the field and become the legitimate owner of the treasure. Likewise, the merchant who discovers the perfect pearl sells everything he owns so that he can possess it. In both cases, these fortunate finders gladly and eagerly exchange their lifetime of earnings for the right to be called the owner of a treasure of surpassing worth. The treasure they discover changes their entire conception of reality. Everything they accumulated up until the moment of their discovery is now unimportant. All that matters is obtaining the one thing that they can’t live without.
This is how we are to respond to the coming of God’s kingdom. Whenever we hear the promises given in the gospel--when they come to us through the preached word or through the administration of the sacraments--they should strike our ears and hearts in such a way that we would eagerly and gladly forsake everything earthly for the sake of owning a share of this heavenly promise. This is because the kingdom of God that is promised to us in the gospel is a treasure unlike any other. It alters our reality—or rather, in finding the kingdom of God we discover what true reality is. To have the kingdom of God is no less than to have what God himself possesses. Whoever finds this treasure discovers that he has found forgiveness of sin—pardon and peace with God—eternal life that he can never lose. The only fitting response to such a life changing discovery is joy.
 Luther's Large Catechism 3.55