2Thessalonians 2:5 Remember ye not, that, when I was yet with you, I told you these things?
Paul now reminds these believers that he had already taught them specifically concerning these events when he was with them. They should remember this.
2Thessalonians 2:6 And now ye know what withholdeth that he might be revealed in his time.
“withholdeth” = to hold down (fast)…. retain, seize on, stay.
These seemed to be the best choices from the Greek looking at the context of the passage. Who is the person about whom they are discussing his being revealed? The man of sin (cf v3). The context indicates that something or someone is keeping his identity secret until it is “his time.” This also indicates that he, the man of sin, has an appointment with destiny, a “set time” (from the Greek). Since we know that the “man of sin” will get his power from Satan (as shown above), this withholding force evidently has the authority to limit the power and authority of Satan. Since Satan is a supernatural entity, the force that limits him must be a supernatural entity of greater power and authority. According to Paul, the Thessalonians knew the identity of this being—the Holy Spirit.
I found a quote from R. A. Coombes at www.aoreport.com that gives further explanation on the grammar used in this verse: “The neuter participle ‘what withholdeth’ in verse 6 becomes the masculine participle ‘he who now letteth’ in verse 7. The first term focuses on the force of the one that restrains, the second on the person that restrains.”
2Thessalonians 2:7 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
“the mystery of iniquity” – Satan’s power and authority, to limited degree, is already effectively at work on planet earth. The fact that it is described as a mystery (secret) is because he has not been allowed to manifest himself openly in the fullness of his power and authority. He has had to be content to work behind the scenes. The Greek word translated “letteth” is the same word translated “withholdeth” in verse 6. The context is clear that this being is restraining or limiting the power and authority of Satan by His presence. The fact that “He” must be taken out of the way indicates that He is a presence that must be removed. Logic concludes that the Holy Spirit is the person of Almighty God that is now “present” on planet earth because He indwells every believer.
Romans 8:11 “But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you.”
When the Holy Spirit is taken away, the believers whom He is indwelling will be taken away. In his later letter to the Ephesians Paul makes it clear that the Holy Spirit is the down payment (so to speak), the earnest of our inheritance to come.
Ephesians 1:13-14 “In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.”
When Jesus taught of the coming of the Comforter, the Holy Spirit, He was clear that He would abide with us forever.
John 14:16-17 “And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.”
“abide” = continue, be present, remain