In Psalms 119:29-30, he wanted to put false ways far from him, for God to be gracious to him by teaching him to obey the Law of Moses, and he chose the way of faith by setting it before him, so this has always been the one and only way of salvation by grace through faith. In Jeremiah 31:33, the New Covenant involves God putting the Law of Moses in our minds and writing it on our hearts, so those who the position that the Law of Moses has been set aside is also the position that the New Covenant has been set aside.
Notably none of those verses say that the Law of Moses has been set aside.
It was in accordance with God's righteousness to be a doer of charity before God made the Mosaic Covenant, so that covenant becoming obsolete does not mean that it is no longer in accordance with God's righteousness to be a doer of charity. While God's covenants include instructions for how to be a doer of His righteousness, the way to do that is based on God's righteousness, not on any particular covenant. God's righteousness is eternal (
Psalms 119:142), therefore any instructions that He has ever given for how to be a doer of His righteousness are eternally and cumulatively valid (
Psalms 119:160). If God were to give two people different sets of instructions for how to be a doer of His righteousness in different situations, then all of those instructions would have the same trait in common, and all of them would be eternally and cumulatively valid for a third person whose goal is to know God by being a doer of His righteousness even though God did not directly give them any instructions. The only way that eternal instructions for how to be a doer of God's righteousness can be set aside would be by first setting aside God's eternal righteousness, and the same is true for God's other character traits.
God has not commanded anything that is not in accordance with walking in the Spirit, but rather Jesus set a perfect example for us to follow of how to walk in the Spirit by walking in sinless obedience to the Torah. In
Acts 5:32, the Spirit has been given to those who obey God. In
John 16:13, the Spirit has the role of leading us in truth, in
Ezekiel 36:26-27, the Spirit has the role of leading to obey the Torah, and in
Psalms 119:142, the Torah is truth. In
John 16:8, the Spirit has the role of convicting us of sin, and in
Romans 3:20, it is by the Torah that we have knowledge of what sin is. In
Romans 8:4-7, Paul contrasted those who walk in the Spirit with those who have minds set on the flesh who are enemies of God who refuse to submit to the Torah. In
Galatians 5:16-23, Paul contrasted with desires of the flesh with the desires of the Spirit and everything that he listed as works of the flesh that are against the Spirit are also against the Torah while all of the fruits of the Spirit are aspects of God's character that the Torah was given in order to teach us how to embody. For example, love is one of the fruits of the Spirit and the greatest two commandments of the Torah are to love God and our neighbor.
Romans 2:25-29, the way to recognize that a Gentile has a circumcised heart is by observing their obedience to the Torah, which is the same way to tell for a Jew (
Deuteronomy 30:6), and circumcision of the heart is a matter of the Spirit, which is in contrast with
Acts 7:51-53, where those who have uncircumcised hearts resist the Spirit and do not obey the Torah.
In
Romans 10:5-8, Paul referred to Deuteronomy 30 as the word of faith that we proclaim in regard to proclaiming that the Torah is not too difficult for us to obey and that obedience to it brings life and a blessing while disobedience brings death and a curse, so choose life! In
Deuteronomy 32:46-47, the Torah is our very life. In
Proverbs 3:18, it is a Tree of Life for all who take hold of it. In
Proverbs 6:23, for the commandment is a lamp and the teaching a light, and the reproofs of discipline are the way of life. In
Matthew 19:17, Jesus said that the way to have eternal life is by obeying God's commandments. In
Luke 10:25-28, Jesus affirmed that the way to inherit the gift of eternal life is by obeying the greatest two commandments of the Torah. In
Hebrews 5:9, Jesus has becoming a source of eternal salvation for those who obey him. In
Romans 2:6-7, those who persist in doing good will be given eternal life. In
Romans 6:19-23, we are no longer to present ourselves as slaves to impurity, lawlessness, and sin, but are now to present ourselves as salves to God and righteousness leading to sanctification, and the goal of sanctification is eternal life in Christ, which is the gift of God, so being a doer of the Torah is God's gift of eternal life.
So 2 Corinthians 3:6 needs to be understood in light of the other verses that says that the New Covenant involves following the Torah, that the Spirit has the role of leading us to obey the Torah, and that being a doer of the Torah is the gift of eternal life rather than a way that contradicts them. If the letter referred to correctly doing what God has commanded and that leads to death, then that would mean that God would be misleading us and shouldn't be trusted, but rather there is something deficient about following the letter that causes the Torah to lead to death rather than life.
Paul and Christ both set examples for us to follow of how to live in obedience to the Law of Moses (Acts 24:14) and we should be intimidators of Paul as he is of Christ.
