A new missions team, and new mission.
Paul and Silas, (who chose to remain at Antioch after seeing the work going on there,) now venture out specifically to revisit the church plants Paul and Barnabas had begun on their first mission trip.
This would mean returning to the exact places Paul and Barnabas had been threatened with being stoned, and to the place Paul was stoned and left for dead. (I personally believe he was dead and raised to life.)
Paul knows this about this trip very well. Silas knows this about this trip from hearing Paul describe what happened. Given this, both men are showing amazing courage, and that they are both completely yielded to the direction of the Holy Spirit. This is what missions work absolutely requires – especially due to the intense nature of spiritual attack those on mission trips are likely to experience. This was exponentially more intense due to it being the foundation of the worldwide church being laid. Satan would not be reticent to attack.
Paul knew this. He understood the nature of spiritual attack, perhaps to a greater degree than any natural man who ever lived. The reason is because he was the tip of the spear, the head of the advance, the beginning of all to follow. Paul wrote much about spiritual attack, and how to resist it, and most likely learned this by the experiences he encountered with Satanic on these earliest of mission trips.
To head out on the first trip was brave because it meant heading out into the unknown. To head out a second time was doubly brave because it meant heading into the known. They knew they would likely be the violent target of much hostility.
Most people would turn away from such an assignment, but not Paul and Silas. They trusted the word of the Lord Jesus Christ – that He would protect them. (Matt 28:18-19, Mark 16:17-18.)
Fear of failure would have been difficult enough to overcome, but fear of brutality, imprisonment, persecution, and death would have also been present. Still they proceeded. Had they accomplished nothing else this alone would have been greatness.