Jesus saves us from our sin (Matthew 1:21) and it is by the Mosaic Law that we have knowledge of what sin is (Romans 3:20), so Jesus graciously teaching us to be does of it is intrinsically the way that he is giving us his gift of saving us from not being doer of it. If you don't think that you need to be saved from not being a doer of the Mosaic Law, then why do you think that you need salvation?
Do you have any ides what your talking about when you mention the Mosaic law?
In 1 Corinthians 9:9-10 and 1 Timothy 5:18, the apostle Paul uses the law shown below.
Deuteronomy 25:4
You shall not muzzle an ox when it is treading out the grain.
To argue that those who labour for the gospel, evangelists, ministers, inquisitors, are entitled
to financial and material support from the church they serve.
Paul uses this phrase to illustrate that the worker deserves to partake in the fruits of their labor,
and it directly influences the understanding that Moses wrote about Jesus.
John 5:46
For if you believed Moses, you would believe Me, for he wrote about Me.
By showing that even the ancient law was designed with a higher spiritual application in mind.
Paul argues "Is it for oxen that God is concerned?"
The idea that Moses wrote about Jesus must be enforced in any reading of the law.
The law is not a set of written rules but a complex prophetic discourse on Christ and
the church.
In 1 Timothy 5:18, Paul quotes Jesus in "The worker is worthy of his wages" (Luke 10:7).
Christians are the "threshers" that do the work of spreading the gospel.
Paul is saying that Moses was writing with an eye toward the future ministry of the gospel.
Paul demonstrates that the Old Testament is not obsolete but contains principles that, when
interpreted through the lens of Christ, are meant for the encouragement and guidance of the Church.
In essence, Paul "unmuzzles" the law from its purely literal reading, to show that it was always
intended to point toward, that deeper spiritual understanding.