Acts 18:19

‘And they came to Ephesus, and he left them there, but he himself entered into the synagogue, and reasoned with the Jews.'

On arrival in Ephesus Paul clearly said his ‘goodbyes' to Priscilla and Aquila. ‘He left them there' suggests that he did not expect to meet up with them again in Ephesus because he expected to embark at once. It would seem, however, that discovering that he could not embark as soon as he had expected he had to take up short term lodgings in Ephesus by the harbour, in order to wait for a suitable berth. This would be why he was unexpectedly able to go to the synagogue to reason with the Jews (we may presumably read in, ‘on the Sabbath day'). We say unexpectedly because had he been expecting it presumably he would have asked Priscilla and Aquila to accompany him.

This first act of evangelising in Ephesus is probably intended to stress that prior to the soon to be explained ministry of Apollos, there had been there an Apostolic witness. Thus the initial action in establishing the church at Ephesus had been Paul's. He could therefore be seen as the founder of the church.