"And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness." (Romans 8: 10)
Righteousness is essential for us, and for two reasons.
Without His righteousness, we remain dead, as Paul writes above. We have life because of righteousness.
"As righteousness tendeth to life: so he that pursueth evil pursueth it to his own death." (Proverbs 11: 19)
"In the way of righteousness is life; and in the pathway thereof there is no death." (Proverbs 12: 28)
"He that followeth after righteousness and mercy findeth life, righteousness, and honour." (Proverbs 21: 21)
So, men need righteousness to live.
Why are we dead, though? Because of sin:
"12Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned: 13(For until the law sin was in the world: but sin is not imputed when there is no law. 14Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come." (
Romans 5: 12-14)
What the first Adam, the Second Adam undid and surpassed:
"15But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many. 16And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification. 17For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ." (Romans 5: 15-17)
Today, we live and reign in life because of the righteousness of God, given to us as a gift, paid for by the death and resurrection of Jesus Christ:
"24But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; 25Who was delivered for our offences, and was raised again for our justification." (Romans 4: 24-25)
"Who shall lay any thing to the charge of God's elect? It is God that justifieth. 34Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us." (Romans 8: 33-34)
Today, we live because of His righteousness, and in Christ we are made the righteousness of God in Christ (2 Corinthians 5: 21)