When we come across professing Christians who perform miracles, we may think they’re worth following by warrant of their miracles. But hold on a minute… just because they perform miracles doesn’t mean they’re worth following. Moses knew that with the magicians of Pharaoh’s court who managed to turn sticks to snakes and water to blood. I don’t think they were conjuring-tricks; I think they were true miracles performed by demonic powers. And we see the same in our own day, which means that the Lord Jesus Christ will return at any time, since we’ve seen so much of this already.
Now, some go to the other extreme and as soon as they hear of a miracle taking place, they assume that this must be a false-teacher. We’re not told to assume that either.