First Thessalonians is most likely the first of the apostle Paul’s letters to become part of the Bible canon and, with the probable exception of Matthew’s Gospel, the first book of the Christian Greek Scriptures to be put into writing.

 Paul established a Christian congregation in Thessalonica when he visited there about 50 C.E. during his second missionary tour. (Ac 17:1-4) Practically from the beginning, that new congregation experienced persecution. (1Th 1:6; 2:14; 3:3-5) Mob violence made it necessary for the brothers to send Paul and his companion Silas to Beroea by night, apparently for the sake of the congregation and the safety of the two men. (Ac 17:5-10) After that, Paul tried twice to visit the Thessalonians, but he said: “Satan cut across our path.” (1Th 2:18) Then he sent Timothy to comfort and strengthen the Thessalonian Christians. When Timothy returned with a good report, Paul was moved to write the Thessalonians a letter to commend and encourage them as well as to give them counsel on certain matters.​—Ac 18:1, 5; 1Th 3:1-3, 6; 4:1, 2.

 The topics of Christ’s return, his presence, and Jehovah’s day seem to have especially appealed to the persecuted Thessalonians. Paul makes frequent references to these topics in his two letters to them. He mentions Christ’s presence six times (1Th 2:19; 3:13; 4:15; 5:23; 2Th 2:1, 8), whereas in all his other inspired letters, he mentions it only once (1Co 15:23). And only in the letters to the Thessalonians does he speak of “Jehovah’s day” or “the day of Jehovah.”​—1Th 5:2; 2Th 2:2.

 Paul places a noteworthy emphasis on prayer. He, along with his fellow workers, always remembered the Thessalonians in prayer (1Th 1:2; 2:13), and the apostle encouraged them: “Pray constantly. Give thanks for everything” (1Th 5:17, 18), and “Brothers, keep praying for us” (1Th 5:25).

 Paul also commends the Thessalonians for their faith, love, and hope. He exhorts them to continue to cultivate these qualities.​—1Th 1:3, 8; 3:10, 12; 5:8.

 The letter is mentioned by name in many of the earliest catalogs of the inspired Scriptures, including the Muratorian Fragment. First Thessalonians is either quoted from or alluded to by several of the early writers, including Irenaeus (second century C.E.), who mentions the letter by name. The papyrus codex known as P⁴⁶, believed to be from about 200 C.E., contains parts of 1 Thessalonians. A papyrus of the third century C.E. (P³⁰) contains fragments of this letter.