Charles Spurgeon Commentary Acts 18:21-23

"but taking his leave of them, and saying, I will return again unto you if God will, he set sail from Ephesus. And when he had landed at Caesarea, he went up and saluted the church, and went down to Antioch. And having spent some time [there], he departed, and went through the region of Galatia, and Phrygia, in order, establishing all the disciples." — Acts 18:21-23 (ASV)

And he sailed from Ephesus. And when he had landed at Caesarea, and gone up, and saluted the church, he went down to Antioch. And after he had spent some time there, he departed, and went over all the country of Galatia and Phrygia in order, strengthening all the disciples.

For you not only need planting, but strengthening. Young saints, like young plants, need much watering, and Paul took care of them.

Evangelists have not half done their duty when they stir up a community unless they go and seek after those who are converted, to strengthen them. Hence the essential need of a permanent pastorate over churches.