they will pick up snakes [i.e., without being harmed]; and if they happen to drink anything poisonous, it will not harm them; they will place hands on sick people [i.e., with prayer] and they will be healed.”
See, I have given you authority to trample on snakes and scorpions [i.e., to receive protection from accidental contact with venomous creatures. See Acts 28:5] and [to have authority] over all the power of the enemy [i.e., Satan. See verse 18]. And nothing at all will hurt you.
But the natives expected him to swell up [from snake bite] or fall dead suddenly, but after expecting this for a long time and not seeing any harm come to him, they changed their minds and said he was a god.
And the God, who brings peace, will soon crush Satan under your feet [i.e., bring an end to the divisive work of the false teachers there]. May the unearned favor of our Lord Jesus Christ be with you [people].