The teachings of the Kabbalah go back to antiquity.
It is said that even the "sons of the prophets" of the period of the First Temple developed certain mystical concepts that became the beginning of the Kabbalah.
In any case, by the time of the Second Temple, we find many indications of systems of esoteric lore, such as Ma'aseh Breshit (Concerning Genesis) and Ma'aseh Merkavah (Concerning the Chariot), which were passed on orally, from one generation of wise men to the next.
In time, Kabbalah ("that which is received") gradually revealed more of itself.
Basic books were written and circulated, and outstanding figures at various times in history hinted at their relation to the Kabbalah and at the way in which they drew from it.
–Rabbi Adin Steinsaltz
From "The Ari" , p.171 in The Strife of the Spirit by Rabbi Adin Steinsaltz