Many of our evangelical friends maintain that choosing and ordination are the same thing. They believe that the word "ordain" used in scripture simply means "appoint" and nothing more. So in John 15:16, when Jesus said, "I have chosen you and ordained you," what He supposedly meant was that He had chosen His disciples and appointed His disciples.
However, when Jesus referred to choosing and ordaining, He used the word "and" as if these were two separate functions. If one strictly limits the word "ordain" to mean "appoint," the above words of Christ appear redundant. Why would He say "I have chosen you and appointed you"?
There are obviously cases in scripture where ordain means appoint, but in this passage it doesn't make sense. The word "ordain" can also refer to "conferring ministerial authority." Thus, Jesus was actually saying, "I have chosen you and conferred ministerial authority upon you." How was this done?
There was no eyewitness description detailing how Jesus conferred authority, but there are scriptural references that illustrate a New Testament tradition of laying on hands to confer ministerial authority:
And the saying pleased the whole multitude: and they chose Stephen, a man full of faith and of the Holy Ghost, and Philip, and Prochorus, and Nicanor, and Timon, and Parmenas, and Nicolas a proselyte of Antioch: Whom they set before the apostles: and when they had prayed, they laid their hands on them.
Acts 6: 2-6
As they ministered to the Lord, and fasted, the Holy Ghost said, Separate me Barnabas and Saul for the work whereunto I have called them. And when they had fasted and prayed, and laid their hands on them, they sent them away.
Much more could be said about this subject, but we would like for you to remember that laying on hands to confer ministerial authority did not end at the cross. It is still the pattern that we should follow today. That is why the epistle to Timothy commands us to exercise caution in ordaining men to ministry:
Lay hands suddenly on no man, neither be partaker of other men's sins: keep thyself pure.
I Timothy 5:22