When Luke speaks of Paul going on ahead without the rest of the group, and then joining them later at Assos, he is giving us a picture of how the mission of God best proceeds. Paul will not only meet up with Luke and the others, he will pour out his heart to the Ephesian elders. God never intended that mission and ministry would be a solo performance. Jesus’ modeled that in his earthly ministry. We are now his body on earth to carry on his mission. Thankfully we do not have to do that alone.
This is the Holy Spirit at work in the lives of God’s people. It brings Jesus glory. And it brings people to Jesus.