From biblical meekness, Rev. Sang Ho Bae turned his expository study on the beatitudes to the meaning of hunger and thirst for righteousness.

When a person receives Jesus into their heart, a transformation occurs in which the very essence of their being becomes new. Just as a caterpillar becomes a butterfly and not only its appearance but even what it eats changes, so a born-again believer finds that what they think and pursue changes, and they begin to feel spiritual hunger and thirst. Likewise, when a person is born again and becomes a child of God, their thoughts change, their pursuits change, and what their soul desires changes. Just as a newborn baby seeks milk the moment it is born, the children of God seek spiritual nourishment. Spiritual hunger and thirst arise within them.
A born-again believer becomes one who “hungers and thirsts for righteousness.” No matter how abundant the culture and pleasures of the world may be, the soul cannot be satisfied with them. Just as a Korean person, no matter how good the food may be, begins to crave kimchi after a few days without it, the people of God long for the “righteousness” that the soul desires. The righteousness spoken of here is not the moral good deeds that people imagine. The righteousness of God is the righteousness of Jesus Christ Himself. No matter how high a person’s moral standards may be, they cannot become righteousness before God’s standard, and therefore all are unrighteous sinners. Scripture says that among those born of woman there is none righteous and that the human heart is “deceitful above all things and desperately corrupt.” Just as white cannot come from black, true righteousness cannot come from human beings who possess a fallen nature. As the prophet Isaiah said, "All our righteousnesses are like filthy rags.”
Nevertheless, there is the belief that human beings are originally good. Especially as the times grow more evil, this belief in innate goodness gains even more support. The more corrupt society becomes, the more people deceive themselves into thinking they are good. Just as a white garment with stains does not look dirty in the darkness but even appears clean, so an age in which the filthy and ugly hearts and actions of human beings appear to be good is an age of spiritual darkness.
Human righteousness actually blocks the righteousness of God. A person who considers themselves moral does not realize that they are a sinner and therefore does not recognize that they need the righteousness of God. The Jews who kept the Law were like this. Comparing themselves with others, they thought they were righteous and rejected the righteousness of God. Their false righteousness blocked the way to true righteousness. But a person who realizes that they are a totally corrupt sinner cannot help but return to God.
The righteousness that the citizens of heaven long for is not human righteousness but the righteousness that God gives—namely, Jesus Christ. “Christ Jesus… became to us righteousness” (1 Corinthians 1:30). Only the Lord is the true garment of righteousness that can cover our sin and shame. The fig leaf garments made by human beings may cover shame for a moment, but they soon wither. But just as God clothed Adam and Eve with garments of skin, the Lord becomes the garment of righteousness that covers our sin forever.
Those who hunger and thirst for righteousness recognize that they are fundamentally sinners and seek the Lord. They acknowledge that there is nothing good within themselves, and knowing that forgiveness of sins comes only through the grace of the Savior, they rely on the Lord alone. They also long to be freed from the power and pollution of sin. Whenever they see themselves still swayed by the temptations of sin, they deeply desire to remove the sinful cravings within and to be delivered from the defilement of sin.
Those who hunger and thirst for righteousness long to resemble the character of Christ. They are not satisfied merely with having received forgiveness of sins. After forgiveness comes a new thirst. They want to resemble the Lord, to truly become a new person, and to live a holy life. Just as a trout becomes distressed when the water becomes even slightly murky and seeks clear water, so a believer cannot feel at ease when living in sin, no matter how good the outward circumstances may be. Therefore, they long for a pure heart, hate the pride and unclean desires within, and pray that God would create in them a clean heart.
The desire for holiness within a Christian is clear evidence that the Holy Spirit is at work. Such a desire does not exist in the heart of the natural person. Apart from the Holy Spirit, no one can have a heart that longs to live according to the desires of the Spirit. This spiritual longing continues throughout one’s entire life. The Lord satisfies our longing, and after satisfying it, He gives us an even greater longing, leading us into mature Christian character. And finally, when we enter the Lord’s kingdom, we will attain perfect holiness, no longer troubled by our corrupt nature.