The Bible is divided into the laws of the Old Testament and the laws of the New Testament, so what are the laws of the Old Testament? The Apostle Paul testified that the law he received at Mount Sinai was the Old Testament law.

[Galatians 4:21~24] Tell me, you who want to be under the law, are you not aware of what the law says? For it is written that Abraham had two sons, one by the slave woman and the other by the free woman. His son by the slave woman was born in the ordinary way; but his son by the free woman was born as the result of a promise. These things may be taken figuratively, for the women represent two covenants. One covenant is from Mount Sinai and bears children who are to be slaves: This is Hagar.

The Apostle Paul referred to Abraham's two wives and explained that they were a metaphor for two covenants. According to the Bible, Abraham had a first wife, Sarah, and a second wife, Hagar. Sarah is the mother of Isaac and Hagar is the mother of Ishmael, but Paul explains that these two women are a metaphor for the two covenants. The two covenants in the Bible are the Old and New Testaments. Hagar, who gave birth to Ishmael, is the Old Testament parable of Sinai. And Sarah, who gave birth to Isaac, symbolizes the New Covenant.

Then, what was the covenant received at Mount Sinai? This refers to the Ten Commandments. Around 1500 B.C. Moses and the Israelites were liberated from Egypt. And they received the Ten Commandments on Mount Sinai and made a covenant with God. Therefore, the Ten Commandments are the Old Covenant. Moses built the temple to keep the Ten Commandments, the covenant of God. And he made a box to store the Ten Commandments and put the Ten Commandments in it. The box containing the Ten Commandments is called the Ark of the Covenant. The Ark of the Covenant was kept in a place called the Most Holy.

[Exodus 25:21~22] Place the cover on top of the ark and put in the ark the Testimony, which I will give you. There, above the cover between the two cherubim that are over the ark of the Testimony, I will meet with you and give you all my commands for the Israelites.

God used the Ark of the Covenant stored in the Most Holy Place as his throne, and he reigned over Israel and granted the forgiveness of sins. But sinners could not recklessly enter the Holy of Holies where God is. If he ignores it and enters, he is killed. Aaron's two sons, Nadab and Abihu, also died as a result.

[Leviticus 10:1] Nadab and Abihu were two of Aaron's sons, but they disobeyed the LORD by burning incense to him on a fire pan, when they were not supposed to. Suddenly the LORD sent fiery flames and burned them to death.

After Nadab and Abihu died, God established rules for sinners to enter the Holy of Holies: burnt offerings, new moon offerings, Sabbaths, and the Day of Atonement. God chose the tribe of Levi from among the 12 tribes of Israel to be the priests and ordered the other 11 tribes to give a tenth of their taxes to support the priesthood of the tribe of Levi.

[Numbers 18:21] Ten percent of the Israelites' crops and one out of every ten of their newborn animals belong to me. But I am giving all this to the Levites as their pay for the work they do at the sacred tent.

To summarize what we've covered so far, God gave the Ten Commandments on Mount Sinai, Moses built a temple to house the Ten Commandments, and God had Moses build a temple to be God's dwelling place, where sins were forgiven, but if you entered the holy of holies where God was, you were killed. So they instituted rituals to approach God: the new moon sacrifice, the regular burnt offerings, the Sabbath, and the Day of Atonement. And they collected a tax called a tithe from the other 11 tribes for the sustenance of the priests. So the Ten Commandments, the temple built to keep them, the sacrifices on the Sabbath and the Day of Atonement, and the tithe collected for the sustenance of the priests are closely related in the Old Testament law. So when the Bible says Old Testament, it means the Ten Commandments.   

There were also laws that prohibited eating food from kosher and unclean animals and set a number of conditions for entering God's temple. There are about 500 more laws with the same purpose. We can't come to God in an unclean state, so we need to keep the rituals of purification. So the Old Testament laws were made for entering the temple. God wrote them down in the Five Books of Moses and placed them next to the Ark of the Covenant in the Holy of Holies.

[Deuteronomy 31:26] ."Take this Book of the Law and place it beside the ark of the covenant of the LORD your God. There it will remain as a witness against you.

The hundreds of laws that existed in the Old Testament were incidental to entering the temple where God was, so when the Bible talks about the Old Testament, it refers to the Ten Commandments, the written word of God. The sacrifices, like the Sabbath and the Day of Atonement, are the means by which we keep God's commandments, but they are not the essence of the Old Testament. The essence of the Old Testament is the Ten Commandments, which contain God's word of promise.