1 Tesalonicenses 1:9

Other people were telling Paul how effective his readers had become at spreading the gospel since they had heard it from him. They reported how the Thessalonians had turned from idols to serve the only divine and true God (cf. Titus 2:11-13). This was the evidence of their faith and love (1 Thessalonians 1:3). [Note: For a good explanation of the relationship between repentance and faith, see Charles C. Ryrie, So Great Salvation, pp. 91-100.] This reference indicates a sizable Gentile population in the church since idolatry was a Gentile vice. There were evidently two types of Gentiles in the Thessalonian church: pagan Gentiles who had been idolaters and God-fearing Gentiles (cf. Acts 17:4).

"The language of separation occurs with regularity in the Thessalonian correspondence (1 Thessalonians 1:9; 1 Thessalonians 4:5; 1 Thessalonians 4:7; 1 Thessalonians 4:12-13; 1 Thessalonians 5:5 f.; 2 Thessalonians 1:7 f.; 2 Thessalonians 2:11 f.; 2 Thessalonians 3:6; 2 Thessalonians 3:14 f.) and serves in a negative way to mark the boundary between those who belong to the Christian community and those who do not, thereby encouraging the new Christian identity. Similarly, the language of belonging is also prominent in the Thessalonian correspondence (1 Thessalonians 1:4; 1 Thessalonians 2:12; 1 Thessalonians 5:5; 2 Thessalonians 1:11-12; 2 Thessalonians 2:6 [sic], 2 Thessalonians 2:13-15;2 Thessalonians 3:16)." [Note: Wanamaker, p. 16.]

Paul’s description of God as living does not simply mean that He is alive; it means that He is also active. He is the true (genuine, Gr. alethinos) God as opposed to false, unreal gods.