Found this explanation: Rabbi Shabbetai ha-Kohen (known by the acronym “the Shach”), a 17th-century commentator on the Code of Jewish Law, writes: "There are those who say that one should wait until the age of 40 before learning Kabbalah, for it says in the Mishnah, ‘Forty is the age of wisdom [binah].’"
But ofc the Crowley branch is a different thing entirely.
Didn't Luria die at 37? When did the 'Kabbalah at 40' rule come into effect?
Found this explanation: Rabbi Shabbetai ha-Kohen (known by the acronym “the Shach”), a 17th-century commentator on the Code of Jewish Law, writes: "There are those who say that one should wait until the age of 40 before learning Kabbalah, for it says in the Mishnah, ‘Forty is the age of wisdom [binah].’"
But ofc the Crowley branch is a different thing entirely.