Genesis 7 includes Hebrew words translated as "clean" and "not clean."
Leviticus 11 includes Hebrew words translated as "clean" and "unclean."
Both "unclean" and "not clean" mean the same thing in English, and they apparently mean the same thing in Hebrew.
Another example is that "uncircumcised" and "not circumcised" mean the same thing in both English and Hebrew. (Genesis 17:14)
Unclean (not-clean) animals were described as detestable in Leviticus Chapter 11.
Nothing unclean was ever meant to be eaten. It is not considered to be food.
Nothing unclean was ever meant to be sacrificed to God. It would be considered detestable.
Sacrifices were always meant to be edible (clean).
When Antiochus Epiphanes sacrificed a pig (an unclean animal) on the Altar of God, it was referred to as the transgression of desolation in Daniel 8:13.
Why God chose to use "not clean" in one passage and "unclean" in another passage is a question that can only be answered by God Himself.
What can be determined, however, is whether or not Cain, Noah, or anyone else living before the Law was given to Moses, knew the difference between clean and unclean animals.
I agree with the statement that was made on this page, "it's absolutely arbitrary to assume everything God spoke to prophets or Moses was written down."
It is also arbitrary to assume that everything God spoke to Cain or to Noah was written down.
One cannot assume that neither Cain nor Noah knew of God's Laws regarding clean and unclean animals. They both knew God's Laws.
It is evident that God's Laws (including Laws for clean and unclean animals) existed in an oral form (a spoken form) from creation.
The Law existed before it was given to Moses on Mt Sinai.
The Torah (the Law) is the Word of God.
Yeshua (the Son of God) is the spoken Word of God in the flesh. (John 1:14)
Everything that was created was spoken into existence through Yeshua. (John 1:3)
Yeshua (the Word of God) existed before the foundations of the world were laid.
The Law (the Word of God) existed before the foundations of the world were laid.
The Ten Commandments (which are part of the Law) existed before they were spoken by God directly to the children of Israel, and before they were written on stone tablets by the finger of God.
Transgressing the Law (sinning) was condemned before the Law was given to Moses.
Scripture defines sin as transgressing the Law. (1 John 3:4)
Through the Law comes knowledge of sin. (Romans 3:20)
Sin is not counted where there is no Law. (Romans 5:13)
The Law speaks to those who are subject to the law, so that every mouth may be shut and the whole world may become subject to God’s judgment. (Romans 3:19)
If mankind was not subject to God's judgment, there would be no need of the Kinsman Redeemer (Yeshua).
The whole world (everyone who has ever existed) is subject to the Law.
Everyone who has ever existed has sinned. (Romans 3:23, Isaiah 53:6)
Everyone who has ever existed is subject to God's judgment.
Everyone who has ever existed is in need of the Kinsman Redeemer (Yeshua).
There are many examples proving the existence of the Law before it was given to Moses on Mt Sinai.
Both Cain and Abel knew that they should offer sacrifices to God.
Cain knew the difference between acceptable sacrifices and unacceptable sacrifices. God said to Cain, "If you do well, will you not be accepted? And if you do not do well, sin is crouching at the door." (Genesis 4:7)
The sin which was "crouching at the door" was Cain's anger, which led to the sin of murder.
If Laws regarding both acceptable sacrifices and murder did not yet exist, Cain could not have been found guilty of transgressing them (sinning).
Before the flood God said, "the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually." (Genesis 6:5)
Wickedness and evil are defined by the Laws of God.
Noah knew which animals were clean and which animals were unclean.
Noah was told to put 7 pairs of each kind of clean animal, and 2 pairs of each kind of unclean animal on the ark. (Genesis 7:2)
If there was no Law defining clean and unclean, Noah would not have known how many of each kind of animal to put on the ark.
Noah offered some of every clean animal and every clean bird as a sacrifice to God as soon as he got off the ark. (Genesis 8:20)
He would not have known to do this if there were no Laws regarding sacrifices and clean & unclean animals.
According to Genesis 13:13, "the men of Sodom were wicked, great sinners against the LORD."
Sin and wickedness cannot be defined without the Law.
Genesis 25:5 is one of the clearest evidentiary passages proving the pre-Mosaic existence of the Commandments, Statutes, and Laws of God.
God made a covenant with Abraham, and then He reaffirmed that covenant with Isaac. God told Isaac that he would receive all of the promised blessings "because Abraham obeyed my voice and kept my charge, my commandments, my statutes, and my laws." (Genesis 26:5)
What commandments, statutes, and laws did Abraham keep other than THE LAWS of GOD?
God blessed the Sabbath day and made it holy at creation. (Genesis 2:3)
Moses knew to keep the Sabbath day before he was given the Ten Commandments or any of the written Law.
Before the Law was given to Moses on Mt Sinai, the Israelites were given manna to eat in the wilderness. Moses explained to them that there would be no manna on the 7th day of each week, because it was the Sabbath of God. They were to collect extra on the 6th day so that they would have food on the Sabbath. Some of the people went out to gather manna on the Sabbath anyway, but found none. God said to Moses, "How long will you refuse to keep my commandments and my laws? See! The LORD has given you the Sabbath; therefore on the sixth day he gives you bread for two days." (Exodus 16:28-29)
This occurred before the Law was given to Moses.
The Law was not given to Moses on Mt Sinai until Exodus Chapter 19.
Many more such examples can be given.
The Law was given to Adam in the Garden of Eden. While there is no one direct statement in Scripture to verify this, there is plenty of Scriptural evidence as proof.
The Law was confirmed through Noah, then it was confirmed through Abraham, Isaac, and Jacob.
The Law was then dictated to Moses by God, and was written down for a permanent record.
If the Law had not existed before it was given to Moses on Mount Sinai, death would not have reigned from Adam until Moses. (Romans 5:12-14)
It is impossible to say that sin exists without the Law, because without the Law sin cannot be defined.
Without the Law there is no basis for judgement.
Before the Law was given to Moses, if the only two laws that mankind had were to keep the Sabbath Day Holy and "do not eat of the forbidden fruit," then...
Why was Cain's sacrifice not acceptable? (Genesis 4:5-7)
Why was Cain's murder of Abel considered sin? (Genesis 4:8)
Why was Lamech judged as wicked (sinful) for slaying a man? (Genesis 4:23-24)
Why was the whole world deemed wicked (sinful), leading to the judgement of the flood? (Genesis 6:11-13)
Why was Nimrod's building the Tower of Babel considered wicked (sinful), leading to the dividing of the languages and the continents? (Genesis 10:8-11, 10:25; 11:1-9)
If there was no Law, how were sin and wickedness defined?
What was the basis for the condemnation?
If men did not have the Law, how could they have been held accountable for sinning (transgressing the Law)?
How were Adam, Cain, Lamech, and Nimrod judged as sinful.
How were Enoch, Noah, and Abram (Abraham) judged as righteous?
How would anyone who lived before Moses know what Yahweh wants for mankind if they did not have Yahweh's Law?
How is it that "all have sinned" (transgressed the Law), if there was no Law before Moses?
Men were judged as sinners (transgressors of the Law) because the Law existed during the time from Adam to Moses. Men were held accountable for transgressing the Law (sinning) because they had knowledge of the Law.
If the Law had not existed from creation, it would have been impossible to sin (transgress the Law) before the Law was given to Moses.
No society can exist for long without a moral code, which is defined by the Laws of Yahweh.
Any society that tries to do so will soon self destruct.
Yahweh's Laws are EVERLASTING (SET in STONE).
Yahweh has always wanted mankind to know that He is YHWH, our God.
Yahweh has never wanted mankind to have other gods before Him.
Yahweh has never wanted mankind to take His name in vain.
Yahweh has always wanted mankind to remember the seventh-day Sabbath.
Yahweh has always wanted mankind to honor their father and their mother.
Yahweh has never wanted mankind to murder.
Yahweh has never wanted mankind to commit adultery.
Yahweh has never wanted mankind to steal.
Yahweh has never wanted mankind to bear false witness.
Yahweh has never wanted mankind to covet.
That will never change!