2 Thessalonians 2:1

Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,

Paul's appeal to the brethren is grounded in the coming of the Lord Jesus Christ and in the gathering of believers to Him, which frames his warning about the great apostasy and the revelation of the man of sin. That gathering is the final gathering at Christ's return, when angels gather the elect from every direction. He wrote to Thessalonians whose strong hope in this event made them fear they might not live to see it. Their misunderstanding of instruction they had received led them to believe the Lord would be revealed in the clouds immediately.

Paul did not teach that Christ would come in their day, but framed his appeal around the warning that a falling away and the revealing of the man of sin must occur first. That apostasy had already begun among false brethren in the early church and would develop further. The coming it points to occurs after Satan's deceptive signs and wonders. Therefore believers were not to be shaken or misled by claims that the day of Christ was already at hand, including messages falsely attributed to Paul, nor by claims that the day or hour is known.

The timing is concealed so that believers remain expectant and prepared, looking for that appearing through watchfulness, prayer, patient waiting, and faithful work. In its larger context of verses 1-12, the passage warns that churches which refuse the truth and accept a lie become part of fallen Babylon. Paul's correction of the Thessalonians' error set out the truth about Christ more clearly in a teaching important for all time.