1 Thessalonians 1:7

so that ye became an ensample to all that believe in Macedonia and in Achaia. [Continuing, Paul gives thanks that he has so much evidence of the election of the Thessalonians that it amounts to a practical knowledge of that election. This evidence is threefold: 1. The power with which he and his companions had felt endued when they preached the gospel in Thessalonica, for they had come not as vain "babblers" of empty words (Acts 17:18; Acts 17:32), but as messengers of God speaking truth powerful in itself, and additionally supplemented by the power of the Spirit. 2. The undaunted way in which the Thessalonians had received the gospel, despite the swiftness with which, they had fallen a prey to persecution. 3. The prompt manner in which the gospel had brought forth fruit in their lives. But what does Paul mean by election? Not that rigid, arbitrary choice of God first promulgated by Augustine, and afterwards emphasized by Calvin, for such doctrine was not then known. Such an absolute, unchangeable thing as Calvinistic election could only have been fittingly made known to an apostle by direct revelation, but Paul knew the election here spoken of by mere sensuous evidence. To elect means to choose, and the choosings of God do not annul the free will or agency of man. Thus Israel is chosen (Deuteronomy 7:6); yet afterwards cast off because of unbelief (Matthew 8:11-12). Election is not made absolute by God; on the contrary, the choosing of God requires that we ourselves make our calling and election sure (2 Peter 1:10); it does not make our salvation sure, for as supplemental to it we ourselves must still work out our own salvation with fear and trembling (Philippians 2:12). We may make shipwreck of the faith to which we have been called or chosen (1 Timothy 1:19), and Paul's exhortations suggest that some of these elect in Thessalonica were in danger of doing this-- 1 Thessalonians 4:1-8]