“The Law of Moses” was not Moses’ invention but God’s.
And if ye have erred, and not observed all these commandments, which the LORD hath spoken unto Moses, Even all that the LORD hath commanded you by the hand of Moses, from the day that the LORD commanded Moses, and henceforward among your generations; Then it shall be, if aught be committed by ignorance without the knowledge of the congregation, that all the congregation shall offer one young bullock for a burnt offering, for a sweet savor unto the LORD, with his meat offering, and his drink offering, according to the manner, and one kid of the goats for a sin offering. Numbers 15:22-24
And all the people gathered themselves together as one man into the street that was before the water gate; and they spoke unto Ezra the scribe to bring the book of the law of Moses, which the LORD had commanded to Israel. Nehemiah 8:1
Remember ye the law of Moses my servant, which I commanded unto him in Horeb for all Israel, with the statutes and judgments. Malachi 4:4
The Lord commanded everything Moses gave to the Israelites.
For the law was given by Moses, but grace and truth came by Jesus Christ. John 1:17
In this verse, the word “by” comes from the Greek word “dia” meaning “through,” “a channel.” Moses was only the channel through which God gave His Law; he was not the source of any part of that Law.
The “Law of God” and the “Law of Moses” are not two different laws.
Consider carefully what Jesus was saying in His well-known statement about the Law in the Sermon on the Mount.
Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled. Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven. Matthew 5:17-19
Jesus is implying that the terms “law” and “commandments” are synonymous, and that all that is included in them is permanent and essential (except what Daniel tells us would cease: sacrifice and oblation–Daniel 9:27). Then He goes on to cite examples that include 2 of the Ten Commandments and 4 other items not mentioned in the Ten Commandments.
Ye have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: Matthew 5:21 (the 6th Commandment–Exodus 20:13)
Ye have heard that it was said by them of old time, Thou shalt not commit adultery: Matthew 5:27 (the 7th Commandment–Exodus 20:14)
It hath been said, Whosoever shall put away his wife, let him give her a writing of divorcement: Matthew 5:31 (from the Torah–Deuteronomy 24:1)
Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths: Matthew 5:33 (from the Torah–Leviticus 19:12; Numbers 30:2)
Ye have heard that it hath been said, An eye for an eye, and a tooth for a tooth: Matthew 5:38 (from the Torah–Exodus 21:24; Leviticus 24:20; Deuteronomy 19:21)
Ye have heard that it hath been said, Thou shalt love thy neighbor, and hate thine enemy. Matthew 5:43 (from the Torah–Leviticus 19:18; Deuteronomy 23:6)
There is a very strong implication here that Jesus considered all of the scripture that Moses wrote (especially Exodus to Deuteronomy) to be the Law. The “Law of Moses” and the “Law of God” are not distinctive terms applying to different parts. They both speak of the same thing.
And when the days of her purification according to the law of Moses were accomplished, they brought him to Jerusalem, to present him to the Lord; (As it is written in the law of the Lord, Every male that openeth the womb shall be called holy to the Lord; (Exodus 13:2; 22:29; 34:19; Numbers 3:13; 8:17; 18:15)) And to offer a sacrifice according to that which is said in the law of the Lord, A pair of turtledoves, or two young pigeons (Leviticus 12) . And when they had performed all things according to the law of the Lord, they returned into Galilee, to their own city Nazareth. Luke 2:22-24, 39
These verses apply the term “the law of the Lord” to various statutes regarding the firstborn and purification rites that are not in the Ten Commandments.
He that despised Moses’ law died without mercy under two or three witnesses: Hebrews 10:28
This verse is speaking of the 10 Commandments as “Moses’ law.” (The 10 Commandments carried the death penalty. Other laws allowed a sin offering as a substitute for the sinner.)
From these few examples it seems quite clear that all of the laws, commandments, statutes, judgments, testimonies, or whatever label might be applied to what the Israelites were given while Moses was leading them (recorded for us in Exodus to Deuteronomy), were not partly God’s Law to be perpetuated and partly Moses’ Law to be eventually dispensed with.
Moses didn’t initiate any of the Law; it was (and is) all God’s Law.