1 Corinthians 16:9

for a great door [the common metaphor expressing opportunity-- Acts 14:27; 2 Corinthians 2:12; Colossians 4:3; Revelation 3:8; Hosea 2:15] and effectual is opened unto me, and there are many adversaries. [For this success and the adversaries which it aroused see Acts 19:1-20. For the riot which it afterwards stirred up see Acts 19:23-41. From this paragraph it appears that it had been Paul's plan to visit Corinth, going thither from Ephesus by direct course across the Ægean Sea; and after a brief sojourn there to pass up into Macedonia, and visit Corinth again on the return. This plan he evidently communicated to the Corinthians in that first epistle which is lost (1 Corinthians 5:9). But the evil reports which came to him concerning the conduct of the Corinthian church caused him to change his purpose, and delay his visit, that they might have time to repent, and so escape the severe correction which he would otherwise have felt constrained to administer to them (2 Corinthians 1:23; 2 Corinthians 2:1). Moreover, he reversed his route; coming by Macedonia (Acts 19:21-22), and intending to depart by sea (Acts 20:3). To help bring about a state of repentance, he sent Timothy as a forerunner (1 Corinthians 4:16-21), and sent him by way of Macedonia (Acts 19:22). He now writes that he has thus altered his plans, and that he is coming through Macedonia, and that he will not pay them two cursory visits, but will make them one long one, and probably stay all winter. However, he will not begin this journey until after Pentecost, for the work in Ephesus has become so fruitful as to demand at present all his attention. Paul carried out his plan as here outlined (2 Corinthians 2:13; 2 Corinthians 8:1; 2 Corinthians 9:2; 2 Corinthians 9:4; 2 Corinthians 12:14; 2 Corinthians 13:1; Acts 20:3-6). He suggests their forwarding him on his journey, thus showing his confidence in them, that they would give him this customary proof of affection (Romans 15:24; Acts 15:3; Acts 17:15; Titus 3:13); but intimates, by using "whithersoever," that his course beyond them is uncertain. We find later that he was compelled to change his plan-- Acts 20:3]