The Mishnah in Pirkei Avot (Chapter 1, Mishnah 13) states: “He (Hillel) would say: Whoever does not add shall be gathered, whoever does not learn is worthy of death and whoever uses the crown shall pass.”
Rabbeinu Ovadia of Bartenura explains the phrase “And whoever uses the crown shall pass” refers to one who uses the crown of Torah, the punishment for which is passing away from this world. He then writes as follows: “Additionally, I have heard that the term ‘using the crown’ refers to one who uses Hashem’s ineffable name, the punishment for which is passing on and being lost from the world, i.e. losing one’s share in the World to Come.” This refers to individuals who have learned from the books of the Mekubalim how to use the holy names of Hashem in order to perform supernatural occurrences; such people have no share in the World to Come.
Maran Rabbeinu Ovadia Yosef zt”l has mentioned an incident related to this topic recorded in the Sefer Mitzvot Katan (Mitzvah 3) who writes that once, Rabbeinu Yehuda Ha’Chassid warned his students not to attend the wedding of a certain friend of theirs, for there were bandits on the way and he was concerned that harm would befall them. These students did not heed his warning, for they were well-versed in the holy names and if any harm would befall them, they would immediately be saved by using these names. This is indeed what happened: Robbers attacked them and tried to murder them and steal all of their belongings at which point they uttered Hashem’s ineffable name and the bandits fell dead. Upon returning home after being saved, Rabbeinu Yehuda Ha’Chassid chided them: “What have you done?! You have lost your shares in the World to Come! Your only option is to repent fully and return to that particular place where you were attacked and this time, do not utter Hashem’s name and let yourselves be killed.” Indeed, these students did so and were killed. This story is utterly astounding, for it is completely forbidden for one to go to a dangerous place. Not only does it seem that returning to the dangerous place a second time does not serve as atonement for their sin, it seems that they transgressed another prohibition by giving up their lives for this!
The Tashbetz (Rabbeinu Shimon bar Tzemach, one of the great Rishonim) addresses this question in his commentary on Masechet Berachot (5b) and asks that if going to such a place involved actual danger, what kind of repentance is performing another prohibition? He answers that since the main point of repentance is for one to encounter the same situation one was in when originally having sinned and to overcome one’s inclination and not sin this time around, they therefore had no other choice but to return to the same place in order to pass the test that they were unable to previously. Maran zt”l questions this idea, for in any event, it is still quite difficult to understand how they were permitted to return to that specific place since the Torah states, “And he (man) shall live by them (the commandments of the Torah)” and not die as a result of them, for a man cannot give up his life for something like this! Nothing stands in the way of full repentance and as long as they could not encounter the same situation again, their repentance process is comprised of only remorse and an acceptance never again to return to this sin; actually encountering the same test will be unnecessary. Maran zt”l leaves this question unanswered. This story is also especially surprising, for even when they returned to the place where the bandits were a second time, it seems that they should have uttered Hashem’s ineffable name once again to save themselves from certain death as nothing stands in the way of a life-threatening situation. Indeed, Maran Ha’Chida records in his diary that once, an Arab met him on a forsaken path and wished to kill him and since he was left with no choice, he preempted him and uttered Hashem’s name and killed him first. Without a doubt, this is because one may use the name of Hashem in a life-threatening situation. Thus, we must seriously delve into the story mentioned by the Sefer Mitzvot Katan in order to understand the basis for the ruling of Rabbeinu Yehuda Ha’Chassid.
In any case, this teaches us the severity of using what is commonly referred to as “Practical Kabbalah,” for even if there are individuals nowadays who may know how to use holy names for medical purposes and the like, one should abstain from consulting such witch-doctors who may appear to be Mekubalim and mystical people. One who cherishes his soul should distance himself from such individuals who present themselves as Mekubalim when the extent of their integrity and righteousness is in serious question (“Babas”). Even if in truth they do possess some knowledge about holy names, it is reasonable to say that they are causing great damage by using these names, for this is not child’s play that immediately upon reciting a specific holy name the sick person will be healed immediately; we are dealing with a deep and complex issue and whoever has only slight knowledge of this issue will end up causing much more harm than good. This is besides for the great punishment and wickedness of profaning the name of Hashem in order to promote one’s own name. If an individual requires a blessing for a certain salvation, one should seek out true Torah scholars who are the true authorities of Torah, whom people respect, and whose teachings and paths are logical and understandable, for their prayers will surely be heard by Hashem. Fortunate is one who cleaves to them and reveres them, for doing so is tantamount to cleaving to Hashem’s holy presence.