1 Thessalonians 3:3 - Matthew Poole's English Annotations on the Holy Bible

The apostle had mentioned before his great afflictions, and they knew well what he himself had suffered both at Thessalonica and Berea, Acts 17:1-34, and therefore might fear they might hereupon be shaken in their faith. And Timothy therefore was sent to comfort and establish them: God could do this without him, but the ministry is his ordinance he works by. And when he saith, that no man should be moved, it shows what is a Christian's duty, to be unmoved by sufferings for the gospel. The word here used by the apostle answers another word, used 2 Thessalonians 2:2, which alludes to the waves of the sea shaken by the winds. Fears, and doubts, or hesitations of mind, do move and shake it, which the apostle sent Timothy to prevent, or remove. And besides, he addeth an argument of his own to confirm them, when he tells them, ye know that we are appointed thereunto. The word is used Luke 2:34 1 Timothy 1:9. But he means, we suffer afflictions according to the purpose and intention of God; they come not by chance, or merely from men's wrath and enmity, but from the appointment of God. And whether the apostle speaks only of his own sufferings, and other ministers of the gospel, or of all saints in general, as Acts 14:22 Romans 8:17,36 2 Timothy 3:12, is uncertain; we may well understand it of both; so that he would not have these Thessalonians think it strange, as if some strange thing happened to them, 1 Peter 4:12, whereby to be shaken in their minds.