That the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit.
God is a God of righteousness and justice. His laws are perfect and beneficial, and breaking them is completely opposite of God’s way of love. Sin produces suffering and death.
Fulfilling the righteous requirements of the law includes obeying God’s law with the help of God’s Holy Spirit, through which Christ lives in us and writes God’s laws on our hearts and minds. Christ also paid the death penalty for our sins, since God’s righteous justice also requires the shedding of blood for sin.
For more about righteousness, see “Slaves of Sin or Slaves of Righteousness?”