His resurrection from the dead, Jesus declared that signs would follow those who believed in Him. Scripture never says these signs would ever stop following believers. As Jesus said these things, he gave authority to believers to do these things in His Name. For believers to cast out demons, obviously they must have authority over them. This passage of Scripture speaks of dominion restored to mankind in Christ Jesus.
Believers have authority over sickness, and demons.
We have the right to speak in tongues as the indwelling Holy Spirit gives us the utterance, which lifts us above the limitations of our intellect to guide us in what words to speak in prayer. And this she did for many days. And he came out that very hour. And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance. For they heard them speak with tongues and magnify God.