It is the ministry of the Holy Spirit to reprove sin, righteousness, and judgment. It is not our ministry. We are simply witnesses. A witness is not the judge or the jury. A witness simply relates what he has experienced, thereby providing evidence to the truth of something. We are to witness in word and deed, to the truth of Jesus being alive in us and let God be the one who convicts. We are simply to testify to what we have seen or to what has happened to us.
Some people in their zeal, have gone beyond the witness stage and have tried to bring people under conviction themselves. This is assuming the job that belongs to the Holy Spirit alone. This not only frustrates the witness but it drives many people away from God. We make a very poor Holy Spirit; therefore, we should stick to our job of being a witness and let the Holy Spirit do His job.
Jesus specified an orderly progression in the way we should witness. First we start in Jerusalem (i.e. where we are). Then we go to those nearby (Judaea).
Finally, we take the gospel to every religious and racial group (Samaria) throughout the whole world.
There are some very practical reasons for becoming witnesses in this way.
Jesus testified that a prophet is honored everywhere except in his home town among his family and friends. Typically, at home is the hardest place to witness. Starting with those who know us best will cause us to humble ourselves and give God all the glory. Also, if rejection comes, this tempers us and our witness, so that we will be more effective and more resilient when we go to the outer most parts of the earth.