This post will be addressing the concept of an Oral Torah, its legitimacy, its necessity, and its relationship to Scripture as well as its legal and historical aspects.
I'm creating this post mainly because in Christendom the concept of a divine "Oral Torah" (lit. "Verbal instruction") has been almost completely dismissed as a heretical invention by rabbinical Judaism. But as will be shown in this post, the concept of Oral Torah is found all throughout Scripture.
This can be shown in relation to the Torah of Moses, as we read in Exodus 24:12: ""And the LORD said unto Moses: ‘Come up to Me into the mount and be there; and I will give thee the tablets of stone, and the Torah and the commandment, which I have written, that thou mayest teach them’" (Exo 24:12) with the "tablets of stone" being the Ten Commandments, the "Torah" being God's Law, and the "mitzvah" (commandment) being its oral explanation. And all these are said to be "written" by God within the Ten Commandments as all the Laws of God are implicitly contained in them and may therefore be regarded as having been written on them. But the reason an Oral Torah was needed regarding the nation of Israel was simply to carry out God's Laws. Like how the Torah of Moses says not to do "melakah" on the Sabbath yet it doesn't explicitly list what all counts as "melakah". But the commandment, which is the oral explanation of the Torah, Moses did not reduce to writing, but he charged the Elders and Joshua and the rest of all Israel concerning its observance, as it is said: "All the word which I command you, that shall ye observe to do" (Deuteronomy 23:1); therefore, this word of the commandment is called, "Oral Torah." And the judges and priests of Israel were given oral instruction as a measure to properly instruct and give judgement concerning the children of Israel as it is stated: "If there arise a matter too hard for thee in judgment, between blood and blood, between plea and plea, and between stroke and stroke, even matters of controversy within thy gates; then shalt thou arise, and get thee up unto the place which the LORD thy God shall choose. And thou shall come unto the priests the Levites, and unto the judge that shall be in those days; and thou shalt inquire; and they shall declare unto thee the sentence of judgment. And thou shalt do according to the tenor of the sentence, which they shall declare unto thee from that place which the LORD shall choose; and thou shalt observe to do according to all that they shall teach thee. According to the law which they shall teach thee, and according to the judgment which they shall tell thee, thou shalt do; thou shalt not turn aside from the sentence which they shall declare unto thee, to the right hand, nor to the left" (Deut 17:8-11).
Both the legal and historical aspects of the Oral Torah can be compared to the heading of an article and the article itself with the heading being the Holy Writings as the summarization of the article (the Oral Torah - its verbal explanation).
Accordingly, before Moses, many of the commandments pertaining to teachings of morality and dietary issues were taught orally from the time of Adam and Noah though it is not explicitly stated in Scripture. Proof of this can be found in Genesis 7:2: "Of every clean beast thou shalt take to thee [Noah] by sevens, male and female: and of beasts that are not clean by twos, male and female." This dialogue presumes that Noah already knows what kind of animals are considered clean and what animals are not. This was later carried on and recorded in the Torah of Moses in Leviticus 11.
However, it must be noted that the "traditions of the elders" as discussed in the Gospels are not to be revered as God's commandments as they were not instituted by divine inspiration (i.e. through God's appointed prophets, apostles, and judges) but by men who thought themselves as God's representatives though they were self righteous and who ended up putting heavy burdens on the children of Israel with their man-made commandments which would indeed sometimes end up leading to the breaking of God's actual commandments. The classic Talmudic example of Jewish rabbis placing unnecessary burdens on the people is found in Shabbat 13 where the sages are quoted as encouraging a Nazirite to detour around a vineyard. It is not forbidden for a Nazirite to walk through a vineyard. However, if he does not walk through it it will be easier for him to resist the temptation of taking and eating from its grapes, something absolutely forbidden to him by Torah law. Yet God did not command that Nazirites had to detour around a vineyard but that they simply couldn't eat grapes. It's an unnecessary additon to God's actual commandment.
The concept of Oral Torah from God in the Bible which is not explicitly written can also be found in Genesis regarding the tree of the knowledge of good and evil. In Genesis 2:16-17 we read: "And the Lord God commanded the man, saying, Of every tree of the garden thou mayst freely eat: but of the tree of the knowledge of good and evil, thou shalt not eat of it: for on the day that thou eatest of it thou shalt surely die." Yet when Eve is having a dialogue with the serpent Scripture says: "And he said to the woman, Has God said, You shall not eat of any tree of the garden? And the woman said to the serpent, We may eat of the fruit of the trees of the garden: but of the fruit of the tree which is in the midst of the garden, God has said, You shall not eat of it, neither shall you touch it, lest you die" (Gen 3:2-3). So we can see here how God (according to Eve) commanded them not to eat or touch the tree of the knowledge of good and evil yet previously in Genesis chapter two it was only recorded that God commanded them not to eat it.
Another reason the Oral Torah was necessary was simply because of the way the Hebrew language was originally written in that it didn't have any vowels. The vowel system in Hebrew wasn't invented until centuries later in 600-1000 AD which is why you don't see any Dead Sea scrolls of the Hebrew Bible with those little dots (such as in אֱלֹהִ֑ים) which are the vowels. And if you've ever tried reading English without vowels you can understand the difficulty of trying to figure out what the words actually say which can in turn completely change the meaning of the text. It's like you know you have "did," "dad," "dead," etc which are only distinguished by the vowels. A perfect example of this in the Hebrew Bible can be found in Exodus 23:19 which says that you cannot seethe a young goat in the milk of its mother. The Hebrew word for "milk" is "חָלָב" (chalab). But the word "fat" in Hebrew is "חֵ֫לֶב" (cheleb). Now if take the away all the dots and dashes around the consonants that you see that these both share (חלב) you're left with the exact same word in the original text which both make sense in the context. The only way you would know the difference if you had the Oral Torah. Therefore the whole vowel system of the Hebrew text which translators use is completely Oral Torah.
The Oral Torah can also be found in the words of Jesus. We read in Matthew 5:27-28: "You have heard that it was said, ‘Thou shall not commit adultery,'" yet Jesus continues: "Moreover I say to you that everyone looking upon a woman to lust after her already has committed adultery with her in his heart." Thus Jesus defines what it means to commit adultery and expounds upon the meaning of this commandment in the Torah of Moses. This is the Oral Torah. Though it shouldn't be concluded that what we find in Matthew 5:27-28, other verses in the same chapter, and elsewhere in Scripture contain all of the records of the stories regarding the King Messiah and his teachings for the Apostle John says: "Now there are also many other things that Jesus did, which if every one should be written, I suppose not even the world itself to have space for the books to be written" (John 21:25). The Apostle Paul says in Acts 20:35: "In everything I showed you that by thus straining, it behooves [us] to aid those being weak, and also to remember the words of the lord Jesus, how he himself said, 'It is more blessed to give than to receive'" - yet this occurrence cannot be found in the Gospel record but was instead taught orally by the Apostles as were all of the records of the life of Jesus until they were committed to writing. And furthermore the Apostle Paul also says: "So then, brothers, stand firm and hold fast to the traditions that you were taught, whether by word, or by letter from us" (2 Thessalonians 2:15). And he also talks about Jannes and Jambres opposing Moses in 2 Timothy 3:8 which cannot be found in Scripture but is another example of a factual story being passed down orally from generation to generation. But if we were to take what the Apostle John says in John 21:25 and apply it to all of God's prophets and apostles we would soon have a massive collection of information regarding the teachings and the history of God's revelation (albeit we don't know all the information). It is according to this Biblical philosophy that makes the Oral Torah legitimate both in its legal and historical aspects.