If you read the next verse of Scripture:<quoted text>
I have given you this definition over and over....
The "why" is found in Scripture 2Th 2:1-14....but you will not understand it because: But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
"So, then, brethren stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter." (2 Thess. 2:15)
It's very difficult to understand why Paul would be telling the faithful to adhere to Jewish traditionary law as you claim. He is, instead, referring to the new traditions taught by "us either by word of mouth or by letter.". Since that's exactly what Paul says I don't understand why you think he might be referring instead to "Jewish traditionary law" as you claim.
Perhaps you could explain yourself?