I Thessalonians 5:2

as a thief in the night--The apostles in this image follow the parable of their Lord, expressing how the Lord's coming shall take men by surprise (Mat 24:43; Pe2 3:10). "The night is wherever there is quiet unconcern" [BENGEL]. "At midnight" (perhaps figurative: to some parts of the earth it will be literal night), Mat 25:6. The thief not only gives no notice of his approach but takes all precaution to prevent the household knowing of it. So the Lord (Rev 16:15). Signs will precede the coming, to confirm the patient hope of the watchful believer; but the coming itself shall be sudden at last (Mat 24:32-36; Luk 21:25-32, Luk 21:35).

The apostle, having spoken in the end of the foregoing chapter concerning the resurrection, and the second coming of Christ, proceeds to speak concerning the uselessness of enquiring after the particular time of Christ's coming, which would be sudden and terrible to the wicked, but comfortable to the saints (Th1 5:1-5). He then exhorts them to the duties of watchfulness, sobriety, and the exercise of faith, love, and hope, as being suitable to their state (Th1 5:6-10). In the next words he exhorts them to several duties they owed to others, or to one another (Th1 5:11-15), afterwards to several other Christian duties of great importance (Th1 5:16-22), and then concludes this epistle (Th1 5:23-28).

5:2 For you know quite well: Paul reminds them of the teaching they had already received (3:3-4). • The day of the Lord’s return is the time when God will come to judge humanity (Isa 13:6, 9; Ezek 30:3) and save his people (Joel 2:21-32; 3:18; Zech 14). • like a thief in the night: Cp. Matt 24:43-44; Luke 12:39-40; 2 Pet 3:10; Rev 3:3; 16:15.