Authority is part of our inheritance in Christ. Jesus said in Luke 10:19, "Behold! I have given you authority and power to trample upon serpents and scorpions, and (phyisical and mental strength and ability) over all the power that the enemy (possesses); and nothing shall by any way harm you."
In Acts 1:8 Jesus said, "But you shall receive power (ability, efficiency, and might) when the Holy Spirit has come upon you, and you shall be My witnesses in Jerusalem and all Judea and Samaria and to the ends (the very bounds) of the earth." (Amp.Bible) These were Jesus's last words to His disciples. These were not words just for the disciples but also for us as His followers.
Jesus has imparted divine authority through the workings of the Holy Spirit in believers. The promise of the Holy Spirit was to give them strength and wisdom and spiritual gifts that they would need on their journey winning souls and healing and delivering souls from the demonic.
We are emissaries for Christ because we represent Him on the earth and as a representative, we are given authority to RE-PRESENT Jesus to the world!!