Many people seem to think that the specific laws and commandments were not given until the children of Israel reached Mt. Sinai.
However we find in Genesis 26 Isaac was told by G-d that he would be blessed because of his father Abraham's obedience to the commandments of G-d.
Genesis 26:3 sojourn in this land,
and I am with thee, and bless thee, for to thee and to thy seed I give
all these lands, and I have established the oath which I have sworn to
Abraham thy father;
4 and I have multiplied thy seed as stars of the heavens, and I have given to thy seed all these lands; and blessed themselves in thy seed have all nations of the earth; 5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.
How then did Abraham know these
commandments? Abraham lived contemporaneously with both
Noah and Shem, and it is reported that Shem ran a College, the College
of Shem and Eber.
Noah was born 1056 from Creation and died in 2006 from Creation.
Shem was born 1558 from Creation and died in 2158 from Creation
Abraham was born 1948 from Creation and died 2123 from Creation.
In fact Abraham had an unbroken
chain of living ancestors going right back to Noah, any of whom
could have passed on to him the Torah as given to Adam, Enosh the son of Seth, lived until the time of Noah, the only ancestor between Noah and Enosh who did not live to see the birth of Noah was Enoch.
Adam was given the six Noahide Laws, the seventh, the prohibition of eating the limb of a living animal was given to Noah, after the Flood.
Since the Oral history was passed on from generation to generation, only those who became idolators did not continue the tradition.
When the children of Israel came out of Egypt they stopped in their journey at a place called Marah where the book of Exodus records that they were given decrees and ordinances and commandments.
Exodus 15:22 Moses caused Israel to journey from the Sea of Reeds and they went out to the Wilderness of Shur; they went for a three day period in the Wilderness, but they did not find water.So it is quite clear that even before the children of Israel reached Sinai they already had a knowledge of the Laws given to Noah. It is equally clear that Jethro, Moses father-in-law knew these statutes also. However the 7 Noahide Laws were given again at Sinai, and because the Jewish people had been declared to be a Kingdom of Priests, and one of the roles of a Priest is to teach, they were given the job of ensuring that these laws be passed on to the Gentile nations. Zech. 8:20-23.
23 They came to Marah, but they could not drink of the waters of Marah, because they were bitter; therefore the named it Marah.
24 The people complained against Moses, saying, "What shall we drink?"
25 He cried to HaShem, and HaShem showed him a tree, he threw it into the water, the water became sweet: There He established for [the nation] a decree and an ordinance, and there He tested it. 26 He said, If you hearken diligently to the voice of HaShem your God, and do what is just in His eyes, give ear to His commandments, and observe all His decrees, then any of the diseases that I place upon Egypt: I will not bring upon you, for I am HaShem, your Healer.