Ex 19.1-6 Story; Israel comes to the wilderness of Sinai and the LORD says his people shall be a kingdom of priests and a holy nation
Ex 19.7-15 Story; The LORD says he will come down on the third say so Israel should be consecrated
Ex 19.16-25 Story; The LORD comes down on the third day and warns the people to remain separate
1) You shall have no other gods before me
2) You shall not make carved images or likeness of any god and serve them
3) You shall not take the name of the LORD your God in vain
4) Remember the Sabbath day and keep it holy (creation and salvation)
5) Honor your father and mother, promise that your days may long in the land God is giving
6) You shall not murder
7) You shall not commit adultery
8) You shall not steal
9) You shall not bear false witness against your neighbour
10) You shall not covet what your neighbour has
Ex 20.18-21 Story; The people fear the LORD, Moses says God is testing them so they may not sin
Ex 20.22-23 Law; Repeated Law on worshipping other gods
Ex 20.24-28 Law; Laws about altars, sacrifices and offerings
Ex 21.1-11 Law; Laws about bondservants
Ex 21.12-27 Law; Laws about human rights
Ex 21.28-36 Law; Laws about agriculture
Passage and Comments
Lots of laws were given in these chapters. But I want to focus on a passage that looks forward to Jesus and his resurrection.
 And the LORD said to Moses, “Behold, I am coming to you in a thick cloud, that the people may hear when I speak with you, and may also believe you forever.”When Moses told the words of the people to the LORD,  the LORD said to Moses, “Go to the people and consecrate them today and tomorrow, and let them wash their garments  and be ready for the third day. For on the third day the LORD will come down on Mount Sinai in the sight of all the people. (Exodus 19:9-11)
Story of Israel
Note the reference to the third day. There is a third day reference in Hosea as well;
[6:1] “Come, let us return to the LORD;for he has torn us, that he may heal us;he has struck us down, and he will bind us up. After two days he will revive us;on the third day he will raise us up,that we may live before him. Let us know; let us press on to know the LORD;his going out is sure as the dawn;he will come to us as the showers,as the spring rains that water the earth.” (Hosea 6:1-3)
Except for Hosea, there doesn't seem to be any other significant references to any particular 'third day' throughout Israel's history.
What is the significance of the third day I am referring to?
Story of Jesus
Jesus was raised and appeared to his people on the third day. Consider the gospel summary;
 For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures,  that he was buried, that he was raised on the third day in accordance with the Scriptures,  and that he appeared to Cephas, then to the twelve. (1 Corinthians 15:3-5)
It is therefore significant to the early Christians that Jesus was raised on the third day. It was alluded to hundreds of years before it happened. From Exodus after delivering his people God appeared to his people on the third day. This represents the establishment of his people. From Hosea the third day signifies people returning to the LORD from exile. On the third day he will raise them up. It is in accordance with these scriptures then that on the third day Jesus was raised from the dead and appeared to his people and through being united in his resurrection have also been raised up to new spiritual life.