How are you getting on sequestering during the COVID-19 pandemic, Petosiris? I hope our conversation is helping you to pass the time in a meaningful fashion. I hope you are able to comfort the sick in some way. (Matthew 25: 35-40.)
How do you claim that the name was to be pronounced only once in the Temple according to the Law when people greeted each other with it in Ruth 2:4?
The Rabbinic ban comes after the 2nd century.
The Torah is not the five books of Moses according to Jews.
What is your source on the rabbinic ban post-2nd century CE?
Again, you want to ensure that you are not lumping all Jewish people together. As I've explained several times, there are significant differences in belief and practice. That Jews are identical and more biblical than modern is unfortunately a common Christian misconception. Not just Reform Jews don't see the Talmud as binding. Judaism has had a number of far-flung splinter groups living in places where the Talmud never reached them.
You are right in some respects. After I said that the prohibition on saying the personal name of God was in the Pentateuch, I thought, "I better check on this, because if it's not, he's going to call me on it."
I spent some time trying to look up the Jewish prohibition on saying the personal name of God. I found many examples attesting that this is the case, and that it was permitted only to the high priest in the Holy of Holies on Yom Kippur. There's no disagreement there.
Some sources said simply that it was a longstanding tradition, but you'd think they could leave a teensy footnote or something.
This one seems definitive:
https://opensiddur.org/prayers/soli...ommandments-and-the-shma-in-the-nash-papyrus/
Apparently the source is the Mishnah, and the practice goes back to about 300 BCE; but with agreement that it ended with the destruction of the second Temple ca. 70 CE. From Rabbi Mark Sameth:
"The Tetragrammaton ...was permitted for everyday greetings until at least 586 B.C.E., when the First Temple was destroyed (Mishnah Berakhot 9:5). In time its pronunciation was permitted only to the priests ..., who would pronounce it in their public blessing of the people. With the death of the High Priest Shimon HaTzaddik circa 300 BCE (Talmud Bavli, Yoma 39b) the Name was pronounced only by the High Priest in the Holy of Holies on Yom Kippur (see Mishnah, Sotah 7:6; Mishnah, Tamid 7:2).... According to the Talmud, the pronunciation was passed on by the sages to their disciples only once (some say twice) every seven years .... Finally, upon the destruction of the Second Temple in 70 C.E., the Name was no longer pronounced at all."
Shimon Ha Tzaddik translates as Simon the Just, or Simon the Righteous.
https://en.wikipedia.org/wiki/Simeon_the_Just If you click on Yoma 39b you will find the reference to the tradition.
The Mishnah, called the Oral Torah (to get back to your original question) is one of the oldest collections of biblical commentaries. Although it was first published in the 2nd century CE, as you suggest, it collated traditions that were often significantly older.
https://www.myjewishlearning.com/article/mishnah/
It is full of examples of the Orthodox belief that one must "put a fence around the law" of more stringent requirements to prevent even accidental violation of the commandments. The original source seems to have been the commandment not to blaspheme with the name of God.