. . And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; [SUP]18 [/SUP]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.
[SUP]19 [/SUP]So then after the Lord had spoken unto them, he was received up into heaven, and sat on the right hand of God.
the "if" in this verse should be understood in "they shall take up serpents" . . . so it would read - "if" they take up serpents, "if" they drink any deadly thing - it shall not hurt them -
It is written thou shalt not tempt the Lord thy God so to intentionally pick up a serpent or to intentionally drink any deadly thing thinking - thinking it will not harm you when that is the natural inclination of a snake and a poison - would be to tempt God. There is an example of Paul accidentally picking up a snack in Acts 28:3 when gathering sticks for a fire -
And when Paul had gathered a bundle of sticks, and laid them on the fire, there came a viper out of the heat, and fastened on his hand. And when the barbarians saw the venomous beast hang on his hand, they said among themselves, No doubt this man is a murderer, whom, though he hath escaped the sea, yet vengeance suffereth not to live. and he shook off the beast into the fire and felt no harm. Howbeit they looked when he should have swollen, or fallen down dead suddenly: but after they had looked a great while, and saw no harm come to him, they changed their minds, and said that he was a god. Acts 28:3-6
Also it needs to be understood that it is questionable as to the authenticity of Mark 16:9-20 because earliest manuscripts and other ancient witnesses do not have these verses. [NOTE: NIV - Some manuscripts have the following ending between verses 8 and 9, and one manuscript has it after verse 8 (omitting vs. 9-20): then they quickly reported all these instructions to those around Peter. After this, Jesus himself also sent out through them from east to west the sacred and imperishable proclamation of eternal salvation. Amen.]