2Thessalonians 2:1-2 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him, That you be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
‘Now we beseech you, brethren …’ This is the 2nd and last New Testament prophecy in 2 Thessalonians that is unfulfilled.
‘By the coming of our Lord Jesus Christ.’ This could refer to both comings – the coming in the air for the saints (1Thess. 3:13; 4:13-18), and the coming of the Lord to the earth with the saints (Matt. 24:3).
The Greek word Parousia means a personal visible presence or reappearing. Two appearances:  Rapture – personal coming in the air (not to the earth) for the saints (1Thess. 2:19; 3:13; 4:13-17; 5:23; 1Cor. 15:23, 51-58; 2Thess. 2:1, 7-8; Jas. 5:7-8; 1Jn. 2:28; John 14:1-3).  Second coming to earth with His saints to reign (Matt. 24:3, 27-51; 25:31-46; Jude 1:14; Rev. 19:11-21; Zech. 14:1-5).
‘Gathering together’ [Greek: episunagoge] is a gathering together in one place (2:1; Heb. 10:25; cp. the verb in Matt. 23:37; 24:31). Here is a gathering together to Him in the air (1Thess. 4:13-18). This could only refer to the rapture, not the second coming.
‘Neither by spirit, nor by word, nor by letter as from us.’ Three things disturbed the Thessalonians: Spirit – spirit-communication, pretended revelation, or spirit demonstration. Word – teaching, preaching, discourse, reasoning, argument, fluent speaking. Letter as from us. False teachers had come to Thessalonica with a letter that had been forged in the name of Paul containing false doctrines about the day of the Lord being at hand (2:2-3).