Luke 9:40

Then he called his twelve disciples together, and gave them power and authority over all devils, and to cure diseases.

And Gehazi passed on before them, and laid the staff upon the face of the child; but there was neither voice, nor hearing. Wherefore he went again to meet him, and told him, saying, The child is not awaked.

And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.