Luke 9

Luke records like Mark of John's inquiry -

"...Master, we saw one casting out devils in thy name; and we forbad him, because he followeth not with us." (New Testament | Luke 9:49)

I would have to assume that John was thinking that this authority and power was only reserved for the twelve Apostles. But the Savior answered -

"...Forbid him not: for he that is not against us is for us." (New Testament | Luke 9:50)

One cannot help but wonder who was the one casting out devils. Was he a baptized member of the Church? Did he hold priesthood authority to do so? In the next chapter of Luke we read that -

"...the Lord appointed other seventy also, and sent them two and two before his face into every city and place, whither he himself would come." (New Testament | Luke 10:1)

"Other seventy" would suggest that a previous seventy had been called and sent - even a first quorum of seventy. One would have to assume that the first seventy were given the same charge as other seventy, to -

"...heal the sick that are therein, and say unto them, The kingdom of God is come nigh unto you." (New Testament | Luke 10:9)

We learn later that this quorum of -

"...seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name." (New Testament | Luke 10:17)

One would then have to assume that the one, saw of John, casting out devils was one of the first seventy called and given authority of the Savior.