New Defender's Study Bible Notes
2:2 day of Christ. Some manuscripts read “the day of the Lord” here, but the meaning would be essentially the same either way. To Paul, “Christ” is “the Lord.”
2:2 at hand. There seems to have been someone in the church at Thessalonica who had represented himself as speaking and writing for Paul, but who had actually subverted Paul’s teachings about the rapture and the day of the Lord. The Thessalonians had become uncertain as to whether the day of the Lord might already be at hand—that is, now happening. This teaching had been especially convincing because of the persecutions they were experiencing. It was necessary, therefore, for Paul to remind them of what he had taught them and provide further information about these great events.