What does “just” mean? Just is Strong’s word, G1342, and it means righteous. Are people righteous? No. Romans 3:10 (CSB), “There is no one righteous, not even one.” 

So who are the just, the righteous ones? They are the true Christians who believe Jesus is their Savior and have given their lives to do God’s will. These have their sins covered by the blood of Christ. 1 John 2:1-2 (CSB), “…we have an advocate with the Father ?– ?Jesus Christ the righteous one. He himself is the atoning sacrifice for our sins, and not only for ours, but also for those of the whole world.” 

Everyone inherits sin and is born dying, because we are all children of  Adam. “As in Adam all die…” 1 Corinthians 15:22. The only way anyone can regain life and made just is through faith in the sacrifice of Jesus Christ. 

John 3:36 (CSB), “The one who believes in the Son has eternal life, but the one who rejects the Son will not see life; instead, the wrath of God (the death sentence) remains on him.” 

Christians stay just or righteous as long as they maintain their faith in Jesus’s sacrifice. If they deny Jesus as their Savior, they will die the second death. Hebrews 10:29 (NKJV), “Of how much worse punishment, do you suppose, will he be thought worthy who has trampled the Son of God underfoot, counted the blood of the covenant by which he was sanctified a common thing, and insulted the Spirit of grace?”

Thus, we become and stay just through our faith that the blood of Jesus covers our sins.