Mark 16:9–20 are the last twelve verses of the Gospel of Mark:
"Now when he rose early on the first day of the week, he appeared first to
Mary Magdalene, from whom he had cast out seven demons. She went and told those who had been with him, as they mourned and wept. But when they heard that he was alive and had been seen by her, they would not believe it. After these things he appeared in another form to two of them, as they were walking into the country. And they went back and told the rest, but they did not believe them. Afterward he appeared to the eleven themselves as they were reclining at table, and he rebuked them for their unbelief and hardness of heart, because they had not believed those who saw him after he had risen. And he said to them:
'Go into all the world and proclaim the gospel to the whole creation.
Whoever believes and is baptized will be saved, but whoever does not believe
will be condemned. And these signs will accompany those who believe:
- in my name they will cast out demons;
- they will speak in new tongues;
- they will pick up serpents with their hands;
- if they drink any deadly poison, it will not hurt them;
- they will lay their hands on the sick, and they will recover.'
So then the Lord Jesus, after he had spoken to them, was taken up into Heaven and sat down at the right hand of God (God the Father). And they went out and preached everywhere, while the Lord worked with them and confirmed the message by accompanying signs." (Mark 16:9–20).
This don't mean intentionally picking up snakes or intentionally drinking deadly poison, but if that happens by mistake, God can take care of you and heal you.
These verses aren't included in two of the oldest and most reliable fourth-century Greek biblical manuscripts; Codex Sinaiticus and Codex Vaticanus. It’s almost unimaginable that the copyists who made them weren't aware of Mark 16:9–20, but they left it out of their Bibles. Modern Bible versions often include it in brackets or footnotes, such as ESV, NLT, NIV, and NASB. Jesus describes there the signs that would follow those who believe him (Mark 16:17–18). It’s important to know that including a note here isn't a recent development in church history. Christians have known for centuries that Mark 16:9–20 may not have originally been part of the Gospel of Mark.
When we look at the manuscripts of the Gospel of Mark that survive today, more than 99 percent contain Mark 16:9–20. This includes not only over 1,600 Greek manuscripts, but also most manuscripts of early translations of the Gospel of Mark.
Further, around 180 AD, Irenaeus unambiguously quoted Mark 16:19 as Scripture in Against Heresies. Justin Martyr and Tatian also knew the verses earlier in the second century. Undeniably, many early Christians considered Mark 16:9–20 to be part of the Gospel of Mark. These persons must have quoted from an earlier manuscript that we no longer have available, older than Codex Sinaiticus and
Codex Vaticanus. This is strong evidence that Mark 16:9–20 was part of the original text, inspired by God. See this explained at time 2:24–4:41 in
Mark 16:9-20 – What Does Jesus Want Me to Do?
My personal opinion is therefore that Mark 16:9–20 was part of the original text, but later wasn't included in Codex Sinaiticus and Codex Vaticanus.
For detailed information, see Was Mark 16:9–20 Originally Part of Mark’s Gospel?
See also Critical verses in the gospels at the end of The Four Gospels.
