Moses gave them the 10 commandments but that was a kind of index or table of contents. The rest of the law laid out all kinds of things for the people to follow. What I'm saying is, this is what Paul is speaking of when he says "of the law". They had all these rules but if one followed them to the T, they were still lost because it had no provision for the removal of sin.
3:23 But before faith came, we were kept in custody under the law, being shut up to the faith which was later to be revealed. 24Therefore the Law has become our tutor to lead us to Christ, so that we may be justified by faith. 25 But now that faith has come, we are no longer under a tutor.
God wrote:
Deuteronomy 10:2 NASB - 'I will write on the tablets the words that were on the former tablets which you shattered, and you shall put them in the ark.'
Deuteronomy 10:3 NASB - "So I made an ark of acacia wood and cut out two tablets of stone like the former ones, and went up on the mountain with the two tablets in my hand.
Deuteronomy 10:4 NASB - "He wrote on the tablets, like the former writing, the Ten Commandments which the LORD had spoken to you on the mountain from the midst of the fire on the day of the assembly; and the LORD gave them to me.
Deuteronomy 10:5 NASB - "Then I turned and came down from the mountain and put the tablets in the ark which I had made; and there they are, as the LORD commanded me."
Moses wrote:
Exodus 24:3 NASB - Then Moses came and recounted to the people all the words of the LORD and all the ordinances; and all the people answered with one voice and said, "All the words which the LORD has spoken we will do!"
Exodus 24:4 NASB - Moses wrote down all the words of the LORD. Then he arose early in the morning, and built an altar at the foot of the mountain with twelve pillars for the twelve tribes of Israel.
Deuteronomy 31:9 NASB - So Moses wrote this law and gave it to the priests, the sons of Levi who carried the ark of the covenant of the LORD, and to all the elders of Israel.
Deuteronomy 31:24 NASB - It came about, when Moses finished writing the words of this law in a book until they were complete,
Deuteronomy 31:25 NASB - that Moses commanded the Levites who carried the ark of the covenant of the LORD, saying,
Deuteronomy 31:26 NASB - "Take this book of the law and place it beside the ark of the covenant of the LORD your God, that it may remain there as a witness against you.
Mark 12:19 NASB - "Teacher, Moses wrote for us that IF A MAN'S BROTHER DIES and leaves behind a wife AND LEAVES NO CHILD, HIS BROTHER SHOULD MARRY THE WIFE AND RAISE UP CHILDREN TO HIS BROTHER.
Luke 20:28 NASB - and they questioned Him, saying, "Teacher, Moses wrote for us that IF A MAN'S BROTHER DIES, having a wife, AND HE IS CHILDLESS, HIS BROTHER SHOULD MARRY THE WIFE AND RAISE UP CHILDREN TO HIS BROTHER.