The JW's claim that modern day miracles (prophesying, healing, tongues) are from the devil. The following is their reasoning why they believe this (from an article on the JW official website). This is rather arbitrary when the cited scripture is read.
The Power of Prayer
Some religions encourage the sick to pray to be healed now, pointing to the miraculous cures that Jesus and his apostles performed. But such miracles were done for a special purpose. They served to prove that Jesus Christ was the true Messiah and to show that God's favor had been transferred from the Jewish nation to the young Christian congregation. Back then, miraculous gifts were needed to strengthen the faith of the newly established Christian congregation. When the infant congregation got on its feet, as it were, and became mature, the miraculous gifts were "done away with."—1 Corinthians 13:8, 11.
8 Love never fails. But whether there are [gifts of] prophesying, they will be done away with; whether there are tongues, they will cease; whether there is knowledge, it will be done away with.
11 When I was a babe, I used to speak as a babe, to think as a babe, to reason as a babe; but now that I have become a man, I have done away with the [traits] of a babe.
Didn't the Pharisees also claim that Jesus' miracles were from the devil, also, didn't Jesus say that they were blaspheming the Holy Spirit when they said this, which is unforgiveable?