II Thessalonians 2:6

now ye know--by my having told you. The power must have been one "known" to the Thessalonians. what withholdeth--that which holds him back; "keeps him in check": the power that has restrained the man of sin from his full and final development, is the moral and conservative influence of political states [OLSHAUSEN]: the fabric of human polity as a coercive power; as "he who now letteth" refers to those who rule that polity by which the great upbursting of godlessness is kept down [ALFORD]. The "what withholdeth" refers to the general hindrance; "he who now letteth," to the person in whom that hindrance is summed up. Romanism, as a forerunner of Antichrist, was thus kept in check by the Romanemperor (the then representative of the coercive power) until Constantine, having removed the seat of empire to Constantinople, the Roman bishop by degrees first raised himself to precedency, then to primacy, and then to sole empire above the secular power. The historical fact from which Paul starts in his prediction was probably the emperor Claudius' expulsion of the Jews, the representative of the anti-Christian adversary in Paul's day, from Rome, thus "withholding" them in some degree in their attacks on Christianity; this suggested the principle holding good to the end of time, and about to find its final fulfilment in the removal of the withholding person or authority, whereupon Antichrist in his worst shape shall start up. that he might be--Greek, "in order that": ye know that which keeps him back, in God's purposes, from being sooner manifested, "in order that he may be revealed in his own time" (that is, the time appointed by God to him as his proper time for being manifested), not sooner (compare Dan 11:35). The removal of the withholding power will be when the civil polity,…

The apostle is very careful to hinder the spreading of an error into which some among them had fallen concerning the coming of Christ, as being very near (Th2 2:1-3). Then he proceeds to confute the error he cautioned them against, by telling them of two great events that were antecedent to the coming of Christ - a general apostasy, and the revelation of antichrist, concerning whom the apostle tells them many remarkable things, about his name, his character, his rise, his fall, his reign, and the sin and ruin of his subjects (Th2 2:4-12). He then comforts them against the terror of this apostasy, and exhorts them to stedfastness (Th2 2:13-15). And concludes with a prayer for them (Th2 2:16, Th2 2:17).

2:6 what is holding him back: This has been variously identified as God, the Holy Spirit, the church, the gospel, Paul, the emperor, the Roman Empire, or the government. Alternatively, the term may refer to something or someone who comes before the man of lawlessness, an agent of the lawlessness active at that time (2:7-8); in Greek literature, this expression could describe demonic possession. This figure would prepare the way for the man of lawlessness when his time comes (2:3, 8).