But you know Timothy's proven worth, how as a son with a father he has served with me in the gospel. (ESV)
There is no greater compliment that Paul could have given Timothy than what we find here in this verse. He is as a son with a father. The Father and Son relationship is the first and most important relationship ever established. What do we see as we look back through all of eternity: God the Father and God the Son.
One of the greatest sacrifices that Jesus made when he came to Earth is that he could no longer enjoy the sweet fellowship with his father. Yet, we have Jesus telling us that he did what he saw the father going. He did what the father told him to do. He demonstrated that perfect relationship of father and son while on this earth.
The Apostle Paul had mentored Timothy and spent so much time with him that Paul viewed him like he was his own son. Paul knew that he could expect Timothy to go to Philippi and bring the very ministry that Paul himself would have brought to them if he were physically able. Timothy had already proven that kind of reliability to Paul
I can think of times that I have asked my father to fill the pulpit for me and preach. After the service there were people who approached me and brought to my attention the many mannerisms and linguistic similarities there were between my father and myself. These were things I had not intended, but they passed on to me because of many years of his leadership and relationship.
You can either be a Timothy or find one. Mentoring others so that they can continue on the work of the ministry of the Gospel is one of the most needed resources for the church today.