Everyone needs someone - a helper - who will be faithful. Timothy was that person to the Apostle Paul.
Paul and Barnabas butt heads over having John Mark join them again on a missionary trip. Later, in 2 Timothy 4:11, Paul calls John Mark "Useful to me for ministry."
Pastor John continues in Acts 15 regarding not adding to Salvation.
Pastor John teaches on Salvation by Grace through Faith - and nothing else.
Pastor John speaks about being Fully Committed.