Or, “in his season,” that is, in the time or season appointed by God, not in a time determined by the “man of sin” himself. The Antichrist will be manifested when the proper time comes. When applied to the historical papacy (see on v. 4) this has been understood to refer to the 1260-year period of domination of that religious power (see on Dan. 7:25; Rev. 12:6). When given the wider application (see on 2 Thess. 2:4) the passage is viewed as referring also to the time when Satan will play a personal role in last-day events only to have his carefully laid scheme for world domination unveiled and its true nature become apparent (see on 2 Thess. 2:4; Rev. 17:16).

 Although Paul does not specifically identify the “he,” the context makes it clear that he is still speaking of the “man of sin” (vs. 3, 4). For comment on “revealed” see on v. 3.

Paul is again reminding his readers of a subject on which they were at least partially informed. Later students of his words have the disadvantage of not knowing the full content of his oral instruction.

 Gr. katechō,“to detain,” “to hold back,”“to restrain.” The phrase is, literally, “the restraining thing,” or “the withholding thing,” being of neuter gender in the Greek. In v. 7 Paul uses a similar expression, but employs the masculine gender, “the withholding one,” or “he who withholds.”

 Commentators recognize great difficulties in vs. 6-12, and trace those difficulties to the fact that Paul is addressing the Thessalonians against a background of previously imparted information, which we do not now possess. Thus any explanation of the passage that is advanced contains an element of conjecture, and must be carefully weighed against the context of Paul‘s message to the Thessalonians.

Some hold that the restraining power is the Roman Empire. Pagan persecutions held in check the tendency of the church to adopt heathen customs and beliefs, and thus held back the appearance of the papacy (GC 49). Probably Paul does not here identify the restraining power because he is dealing with a delicate question on which he dare not be more explicit for fear of bringing further persecution upon his converts should his letter fall into enemy hands.

 Others see a wider application of the phrase. They believe that the masculine form “he who withholds” (see above) refers to God. In such a case “what withholdeth” could be regarded as a reference to the circumstances arranged and permitted by God (cf. on Dan. 4:17) to delay the manifestation of the Antichrist, both in his historical aspect and in his final manifestation yet to come (see on 2 Thess. 2:4). For the manner in which God keeps the powers of evil in check see on Rev. 7:1.