When Paul left Corinth, he sailed to Syria.  He took Aquila and Priscilla with him.  Paul had shorn his head in Cenchera, due to a vow that he had made.  We are not told what this vow was, but it was important to Paul.  We may be around people everyday who have made a vow to God and not know it, but hopefully they will take any vow made to God with the utmost sincerity.  When Paul got to Ephesus, he left Aquila and Priscilla there, but he went to the synagogue and reasoned with the Jews.  Even as he had shifted his emphasis to the Gentiles, he had not given up witnessing to the Jews.  Again, if a particular group does everything they can to stop us from reaching people with the gospel, we cannot give up on them.  The Jews were God's chosen people to represent Him in the world, and when the Messiah came, they failed Him.   By salvation through Christ, we are His chosen people to represent Him in the world today, and hopefully we will not fail Him.  The people in the synagogue wanted Paul to stay longer, but he consented not.  That was a change for them to want him to stay, but he said he needed to keep this feast that cometh in Jerusalem.  We must never let seeming success and the desires of others keep us from following God's leadership.  Paul did tell the people there that he would come to them again, God willing.  As God's people, any promise we ever make must be made based on the will of God.  With his promise, Paul left Ephesus and sailed to Caesarea.