If you try to correct a modern Christian for not keeping commandments of YHWH, this is often a big part of their false doctrine where they say; "By the works of the Law no flesh will be declared righteous", where they imply the law is worthless to us and not to be obeyed.
First off I just want to remind you, why was Yahushua the Messiah declared righteous, and saved all of mankind from death?
Through his keeping of the Law perfectly. He was without sin.
He kept the Law perfectly and did not sin a single time which made him the perfect lamb without blemish that set us free from the curse of the Law!(That is another misconception in itself, you see, the curse of the law is DEATH because those who break it will die, we are pardoned from the death penalty.)
Now let's look at the first place where Paul mentions this topic that men twist and distort to teach lawlessness;
Romans 3:20 "For by works of the Law no flesh will be declared righteous in his sight, since by the Law is the full knowledge of sin"
Now there is a misunderstanding to this because the people are not knowing the context.
So we see what false teachers are saying, but we notice there is a 2nd part to it, Paul tells us why no flesh will be declared righteous in HIS sight through the Law.
Through the Law comes full knowledge of sin!
When we see the righteous Law of YHWH then we realize we are NOT righteous and we are sinners because we are either NOT keeping it, or we have messed up and sinned before!
This is why no flesh is righteous in YAH's sight, because we have all sinned once and fell short of his glory!
Messiah pardoned our former sins and our slip ups.
Now the point of Paul's words is that we are declared righteous by the sacrifice of Yahushua the son of YHWH, not by anything we may do, this however does not mean we can stop obeying the law.
It says nothing like stop keeping the law, read it again and see it does not say stop keeping the law, rather it is just stating a fact our righteousness is a free gift given to us from YHWH and we will fall short if we try to obtain that righteousness any other way because we have all sinned against the law, we have already messed up to where we can not obtain that righteousness through the law in his sight.
Romans 3:23 "For all did sin, and are come short of the glory of Elohim"
Only a few verses later Paul clearly says the law is not done away with and we must keep it.
So what he said may be confusing to some that are not focused, but he lets us know what he is saying and what he is not saying!;
Romans 3:31 "Do we then abolish the Law by this faith? Of course not! Instead, we uphold the Law"
Also the verse says sin is known from the law, and we should all know we must repent from sin and can not continue in sin, so it also in another way teaches us to keep the law of YHWH, here is another verse from Paul;
Hebrews 10:26 "For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins"
He teaches us that we can not go on deliberately breaking commandments or else there no longer remains a sacrifice for our sins!
1 John 3:4 "Whoever commits sin breaks also the Law, for sin is the breaking of the Law"