First, it should be noted that almost all Bible scholars agree that these verses were not originally part of Mark’s Gospel. “The doubtful genuineness of Mk 16 verses 9-20 makes it unwise to build a doctrine or base an experience on them (especially vv. Mk 16:16-18),” points out noted commentator Charles Ryrie. However, those who handle snakes in their worship are not often impressed by what Bible scholars think of the genuineness of Mark 16:9-20. The verses are in the King James Bible, which is the only Bible most of them trust, and for them that is the end of the matter.
But even if these verses were authentic, they do not command the handling of serpents or the drinking of poison, and they say nothing of fire. So they cannot be read as a requirement for worship. In fact, the apostle Paul did encounter a serpent on the island of Malta (Melita, KJ) but only by accident because it was in a bundle of sticks he was laying on a fire. Although Paul was bitten and was divinely protected from harm, he did not pass the viper around for others to hold. Instead, he “shook off the beast into the fire.” Far from feeling a burning pain as modern snake handlers do, he “felt no harm.”—Acts 28:3-6, KJ.