Paradoseis (παραδόσεις) is the Greek word we find in 2 Thes. 2:15 where Paul says, "hold onto those traditions which you have been taught..." What traditions? According to Thayers Greek lexicon Paul is speaking of the Jewish oral traditions and laws passed down from generation to generation. Not having grown up Jewish like Jesus and His Apostles we can learn much from many of these "traditions". You can find things about baptism (known as ritual immersion in a mikvah) or even the Holy Spirit, which is rarely mentioned in the OT, and that is why you can still find today people like those in Acts 19. "We have not so much as heard whether there be any Holy Ghost."
Here is an example from the Mishnah.... regarding Proverbs 15:33 "Heedfulness leads to cleanliness, cleanliness leads to purity, purity leads to holiness, holiness leads to fear of sin, fear of sin leads to [the gift of] the holy spirit, the holy spirit leads to the resurrection of the dead, resurrection of the dead leads to the world to come, and the world to come leads to the Shekinah."
Why does all this occur? Out of reverence, wisdom, honor, and humility; therefore it is said, "The fear of the Lord is the discipline of wisdom; humility precedes honor."
(The Mishnah or Mishna (/ˈmɪʃnə/; Hebrew: מִשְׁנָה, "study by repetition"), from the verb shanah שנה, or "to study and review", also "secondary," is the first major written redaction of the Jewish oral traditions known as the "Oral Torah". It is also the first major work of Rabbinic literature.)
