Acts 8:17 - Albert Barnes' Notes on the Bible

Then laid they their hands ... - This was an act of “prayer,” expressing an invocation to God that he would impart the blessing to “them.” On “how many” they laid their hands is not said. It is evident that it was not on “all,” for they did not thus lay hands on Simon. Perhaps it was done on a few of the more prominent and leading persons, who were to be employed particularly in bearing witness to the truth of the gospel. It was customary to lay the hands on any person when a “favor” was to be conferred or a blessing imparted. See notes on Matthew 9:18.