This question is referring to Matthew 16:18 where Jesus tells his disciples "Everyone who believes me will be able to do wonderful things. By using my name they will force out demons, and they will speak new languages. They will handle snakes and will drink poison and will not be hurt. They will also heal people by placing their hands on them". This statement has been interpreted in a variety of ways by Christians, and so lets investigate if the Bible can explain what Jesus meant.
Why Is This Question Important?
Some Christians claim that if we believe that people can cast out demons, can speak in tongues (other languages), and heal others, that then we should also be able to drink poison and handle venomous snakes and not be hurt. Some atheists use this verse and try to convince Christians that if they drink poison and lives that then the atheist will convert to Christianity. There are even some Christian denominations that go so far as to use snakes in their worship ceremonies. I found a news article which claims that a preacher in the US tried to use a snake during a service and was bitten and died. It says the preacher's wife also died a few years earlier from another snakebite.
So does this mean that the preacher and his wife were not real Christians? Or did Jesus lie when he promised that people who believe in him would be able to do this? Although it is an obscure passage, the implications can be important. If it proves that Jesus lied, then how can we trust everything else he said?
What Else Does the Bible Say?
A similar verse is found in Luke 10:19, where Jesus says "I have given you the power to trample on snakes and scorpions and to defeat the power of your enemy Satan. Nothing can harm you. But don't be happy because evil spirits obey you. Be happy that your names are written in heaven!". However, over the centuries, many Christians have been hurt and killed, which seems to contradict Jesus' statement "nothing can harm you". Therefore, perhaps these verses do not apply in all situations or to all Christians. We should read Luke 10 fully to see what context this verse is written in. Luke 10 tells the story of the 72 disciples (yes, Jesus had more than just 12) who he sent out to the towns in Israel to preach and spread his message. In Luke 10:3-4, before they start their journeys, Jesus tells them "I am sending you like lambs into a pack of wolves. Don't take along a moneybag or sandals.". I believe that this shows that Jesus believed that God would supernaturally protect his disciples while they were on this mission. Later when Jesus sends his disciples out again, he tells them "But now, if you have a moneybag, take it with you. Also take a traveling bag, and if you don't have a sword, sell some of your clothes and buy one." (Luke 22:36). This shows that Jesus told his disciples to take care of themselves and to have a sword for protection. If they needed a sword, then it shows that the previous promise of "Nothing can harm you." was intended as special protection for the 72 disciples only for a specific task.
Also note that in this verse, Jesus warns his disciples to be happy that they are saved, not that they can do all these miracles and are obeyed by evil spirits. I believe this shows that as Christians we should not become proud of our abilities or supernatural gifts, and should only use them to honour God, not ourselves. If a preacher had the gift of healing or casting out evil spirits (or even picking up snakes and not getting bitten) it would be easy to become proud of what they could do. They might start doing it to show off instead of doing it for God's glory.
However, there is other evidence that the original verse in question (Matthew 16:18) about being able to handle snakes and drink poison is true. Starting in Acts 28:3, Paul makes a fire from some gathered wood, but a snake crawls out of the fire and bites Paul. All the people who see this expect Paul to die, but when he doesn't then they respect him and asked him to heal all their sick people, which Paul did, and Paul gained the respect of the local governor. Here, God did supernaturally protect Paul from the snakebite and use it to spread His message, but this was not because Paul purposely went out to handle a snake - it was an accident. There are many other times in the Bible when God supernaturally protects his followers from harm. Earlier in Acts 27, Paul is saved from a shipwreck. There is the story of Shadrach, Meshach, and Abednego who survived being thrown into a burning furnace by king Nebuchadnezzar (Daniel chapter 3) . Daniel is protected from being eaten by lions (Daniel chapter 6). This shows that God does protect his servants when they are in danger. But note that these people never want to be in danger or purposely go out of their way to walk into a furnace or walk into a cave of lions. God has given us a brain and common sense for a reason.
Don't Test God
Jesus specifically says that we should not test God. In Matthew 4:7, Satan tries to get Jesus to jump from the temple, saying that God will send angels to protect him and he won't be hurt. But Jesus' response to Satan was "The Scriptures also say 'Don't try to test the Lord your God'.". If Jesus Himself was not willing to test God, then how much more stupid is it for regular Christians to try?
God Protects People from Danger
I believe that Matthew 16:18 is meant to show that God will protect you from danger which is out of your control, especially when you are doing His work (such as being a missionary, etc.). However, if people are trying to purposely test God, God does not protect them from danger and sometimes God will purposely teach them a lesson, as stated in 1 Corinthians 10:9. Here it describes the actions of the Israelites in the desert with Moses. It says "Don't try to test Christ, as some of them did and were later bitten by poisonous snakes.". But in the original description of the event (see Numbers 21:4-9), the ones that were bitten survived if they had faith and followed Moses' instructions for how to be healed afterwards.
So as Christians, we should not purposely do dangerous things just to try to prove our faith, whether we are trying to prove it to ourselves or to others. It goes against the command not to test God, and seems very arrogant to try if even Jesus would not test God. If we are in danger however, there is plenty of evidence which shows that if we have faith, God will protect us, and often used it to show He really is all powerful (as in the cases of Shadrach, Meshach, Abednego, and David, and others). So don't give in to people who try to get you to test God. If God wants, He's perfectly able to show these people that He does exist, and doesn't require any action from you, except maybe the strength and faithfulness to trust Him in the face of danger.