Acts 18:9-10 ... "And the Lord said to Paul in the night by a vision, 'Do not be afraid any longer, but go on speaking and do not be silent; for I am with you, and no man will attack you in order to harm you, for I have many people in this city.'"
Having established congregations of the Lord's church in Philippi, Berea, and Thessalonica in Macedonia, Paul proceeded on south into Greece as far as the great commercial city of Corinth. He made this trip alone, for Timothy and Silas stayed in Thessalonica to help the church there become stronger. A strange mood seems to have seized Paul's mind as he reached Corinth, for later, when he wrote an epistle to them and reflected on the beginning of his ministry there, he said, "I was with you in weakness and in fear and in much trembling." That mood of apprehension and fear became an impediment to his work for the Lord, so much so that it appears he was reluctant to preach in his usual manner of courageous boldness. The Paul who was fearless to face down an angry mob in Ephesus, (Acts 19:28-31), was afraid to speak out for Christ in Corinth where it seems there had been no resistance or threat against him at all. The text above is the inspired record that the Lord saw the need to speak to Paul in a night vision to boost him out of this trench of fear and encourage him to resume his ordinary style of aggressive evangelism.
We do not know what came over Paul to induce this fearful paralysis. Like Peter walking on the water to Jesus, did he suddenly become self-conscious and begin to think about the waves of potential trouble sweeping all about him? Having disregarded awful dangers in Thessalonica, Philippi, Lystra, Jerusalem and Damascus, did he fail to remember that the Lord was always his companion in spirit? at least until the Lord reminded him in the vision at night? Sometimes God's servants are suddenly gripped by fear for reasons which they themselves do not understand. After a long time of working boldly for the Lord, even against hostile forces, they one day lose courage to do even easy tasks when no opposition faces them. Perhaps it is just a manifestation of our human weakness, facilitated by deepening humility, as we grow in the Christian graces.
The Lord, however, does not want His servants to be hindered by fear for long. A brief bout with this paralyzing emotion is beneficial in teaching the Christian that he ought not "to think more highly of himself than he ought to think," (Rom. 12:3), but when that lesson is learned the mood should be overcome. Something of this sort happened to the prophet Elijah. After a most courageous public ministry in opposition to the king and queen and the prophets of Baal in their promotion of idolatry, Elijah was suddenly terrified when Queen Jezebel threatened his life. In fear he fled Israel and did not stop until he had crossed a barren desert and taken refuge in a cave at Sinai. Then the Lord took measures to snap Elijah out of his mental oppression. "What are you doing here, Elijah?" the Lord twice asked him, (I Kgs. 19:9,13), as though to say, "Elijah, I did not commission you as My prophet to hide in a cave four hundred miles from home!" Then He commanded, "Go, return on your way to the wilderness of Damascus, and when you have arrived, you shall anoint Hazael king over Syria," (I Kgs. 19:15). Although this was a commission to strike fear into the prophet's heart, since Syria was Israel's mortal enemy, Hazael was her military commander, and Elijah was, in effect, inducing a man to overthrow the reigning king and seize his throne, the prophet proceeded to do it fearlessly. The Lord's encouragement indeed "put his heart back into him." The same was the case with Paul in Corinth. And the same will be the case with the timid Christian today who takes his fear to Jesus in prayer.