Forbidden before 40

Is it not forbidden to study the Kabbalah before the age of forty

This decree was canceled about 450 years ago, as it was confirmed and written by Rav Avraham Azulay :

“What was decreed from above; not to study the Kabbalah openly, was for a limited time only, until the end of the year 5260 . From there and after, it was allowed, and from the year 5300 it was decreed that it is a “Mitsvah” (commandment). (Or Ha’Hamah, introduction).

Also two of the most important Kabbalists of all times; the Ari Z’al and the Ram’hal started very young as they both died before the age of forty