Jesus in Mark 16:

15 He said to them, “Go into all the world, and preach the Good News to the whole creation. 16 He who believes and is baptized will be saved; but he who disbelieves will be condemned. 17 These signs will accompany those who believe: in my name they will cast out demons; they will speak with new languages; 18 they will take up serpents; and if they drink any deadly thing, it will in no way hurt them; they will lay hands on the sick, and they will recover.”

Related:
Nightline: Speaking in tongues medical study PROVES Holy Spirit praying
The SCIENCE of Divine Healing – by John G. Lake: “At one time I submitted myself to a series of experiments. It was not sufficient to know that God healed; I had to know how God healed.”
Study: Prayer heals when it’s close-up and personal
How to speak in other tongues as the Holy Spirit leads you
How to speak in tongues as the Holy Spirit enables you
I’ve finally shared much of what I know about and what can be done through the TREMENDOUS and mostly misunderstood and underused gift of tongues.
Jim Feeney: Why Speak in Tongues? (Is Speaking in Tongues of God? Is It for Today?)
A Gift that Will Set Many Free! (A Death Warrant is Out for Your Souls)