It's supposed to be a faith-thing, based on a line from scripture. Snake handlers drink strychnine at their services too; part of the verse not only speaks of being safe from "taking up serpents" but being immune from poison too. Congregants who are bitten, whether they die or not, or are poisoned, are simply accused by their fellow congregants of opening themselves to harm by having lost their faith even if only for a moment.

Pretty silly, isn't it?

I don't understand it either. Wonder if some of it isn't in the translation because God called Satan the serpent.

    And these signs shall follow them that believe: In my name shall they cast out devils; they shall speak with new tongues. They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover. (Mark 16:17-18)

    Behold, I give unto you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt you. (Luke 10:19)

3Paul gathered a pile of brushwood and, as he put it on the fire, a viper, driven out by the heat, fastened itself on his hand. 4When the islanders saw the snake hanging from his hand, they said to each other, “This man must be a murderer; for though he escaped from the sea, Justice has not allowed him to live.” 5But Paul shook the snake off into the fire and suffered no ill effects. 6The people expected him to swell up or suddenly fall dead, but after waiting a long time and seeing nothing unusual happen to him, they changed their minds and said he was a god.

Acts 28: [quote]7There was an estate nearby that belonged to Publius, the chief official of the island. He welcomed us to his home and for three days entertained us hospitably. 8His father was sick in bed, suffering from fever and dysentery. Paul went in to see him and, after prayer, placed his hands on him and healed him. 9When this had happened, the rest of the sick on the island came and were cured. 10They honored us in many ways and when we were ready to sail, they furnished us with the supplies we needed.

I believe (just my opinion) this applies to the early Apostolic Church.  Some (not all) of them underwent some miraculous rescues and their ministry/Apostleship  was confirmed through many signs and wonders.  For example Paul was bit by a venomous snake when shipwrecked on the Island of Malta and the locals thought he was a god.

These signs and miracles were used by God to spread the Gospel and confirm Apostolic authority. (again, JMHO).

They certainly were not to seek poison, or venomous snake for ritualistic purposes.  That of course is  perverse and stupid.