What is the reason that some Sufis are not harmed when iron rods are plunged into their bodies during sessions of dhikr, and what is the ruling on these sessions and joining them?

The aforementioned act is an innovation (bid'ah) that may lead its perpetrator to polytheism (shirk (definition)), for it was not done by the Prophet, peace be upon him, nor his Companions. He, peace and blessings be upon him, said: "Whoever performs an action which is not in accordance with our matter, it will be rejected." Their not being harmed may be due to the assistance of jinn, and it is not an argument for the correctness of their belief, for such an act is performed by disbelievers. This innovation is not among the miracles of the saints (awliya'), because a saint is a devout believer who avoids polytheism and innovation. Allah Almighty says: "Unquestionably, [for] the allies of Allah there will be no fear concerning them, nor will they grieve Those who believed and used to fear Allah."