Some have argued that the righteousness Jesus refers to in Matthew 5:6 is what comes to all through Christ upon repentance. The Bible, though, shows three kinds of righteousness, and each is important in its own right. The first is the righteousness of faith that comes when God justifies a sinner by grace through the redemption that is in Christ Jesus. This results when Christ's obedience is imputed to him, thus giving him legal righteousness before God. David writes in Psalm 14:1, "There is none who does good, no, not one"; Paul changes the wording in Romans 3:10, "There is none righteous, no, not one."
God makes these powerful indictments against a world in which most people undoubtedly consider themselves as "good." But it is a goodness perceived through their own standards - in a mind not awakened to God's righteousness, filled with the pride of self-righteousness, deceived by the ruler of this world (Revelation 12:9; John 12:31). Such a mind can be, like the unconverted Paul, an accomplice in killing and persecuting God's true children and think all the while it is righteously doing God service (John 16:2). They are like those described in Titus 1:16: "They profess to know God, but in works they deny Him, being abominable, disobedient, and disqualified for every good work."
According to God, all of us have been somewhere in this picture. As sinners we frequently broke God's law in word, thought, and deed, and in many cases, were ignorant of doing so because of the deception Satan has wrought. But God in His calling removed the veil that was over our minds and revealed Himself, His purpose, and His standards. We convicted ourselves of spiritual bankruptcy. Where we formerly thought of ourselves as perhaps involving ourselves in a "little" sin - but basically okay as measured against our neighbor and the evil people in society - we now begin to see ourselves in a far different light. We do not have a leg to stand on before God.
Romans 2:4 makes it clear that only by God's mercy are we led to see ourselves to some degree as He sees us: "Or do you despise the riches of His goodness, forbearance, and longsuffering, not knowing that the goodness of God leads you to repentance?" God enables us to measure our goodness, our righteousness - which He describes as "like filthy rags" (Isaiah 64:6) - against Him rather than our neighbor. We realize that certain death for sin is staring us right in the face, yet He has graciously provided us with a perfect righteousness in Christ. This offer is not free, though, because we must totally surrender our lives to His rule. Even as it cost Jesus His life to provide this deliverance, it also costs us our lives, as living sacrifices (Romans 12:1), to take advantage of God's offer. Nonetheless, it is amazing how hungry and thirsty we become for God's offer of justification leading to salvation.
However, we cannot stop here. Hunger and thirst have brought us this far, but it is only a beginning. If it is a true, godly hunger and thirst, it remains, even though we are justified, because the justified person realizes God has only begun a good work in us (Philippians 1:6). The hungry person will recall Romans 5:1-2:
Therefore, having been justified by faith, we have peace with God through our Lord Jesus Christ, through whom also we have access by faith into this grace in which we stand and rejoice in hope of the glory of God.
Justification brings reconciliation and therefore peace with God and access to Him. But it also brings with it the hungering and thirsting for the very glory of God! What an awesome thing to consider that, once we have an imputed righteousness, having God's very image created in us, imparted to us by His Spirit, is the goal of the process we began through God's calling. It can be ours!
It is a profound but nonetheless true purpose that everyone who catches this vision must surely desire with all his being! Have we ever been offered anything greater? Can any other goal in life even begin to compare? We must not "neglect so great a salvation" (Hebrews 2:3)! We must not let this great potential slip from our grasp! No wonder Jesus used such strong language to describe the driving desire for God's righteousness that pleases Him. And when He sees it in us, He will also satisfy it.