2 Thess.2: 6 And you know what is restraining him now so that he may be revealed in his time.
Who is the restrainer??
2Th 2:3 Let no man deceive you by any means:
for that day (the Lord's return) shall not come, except
there come a falling away (ἀποστασία, feminine singular noun) first, and
that man of sin be revealed,
the son of perdition;
2Th 2:4 Who (masculine singular relative pronoun) opposeth and and is exalted above all that is called God, or that is worshipped; so that
he (αὐτὸν, masculine singular) as God sitteth in the temple of God, shewing
himself (ἑαυτὸν masculine singular) that
he is God.
2Th 2:5 Remember ye not, that, when I was yet with you, I told you these things?
2Th 2:6 And
now (because I just told you) ye know
the letting/restraining thing (τὸ κατέχον neuter singular: that there must be a falling away first) for
him (αὐτὸν masculine singular: the man of sin) to be revealed in
his (ἑαυτοῦ singular masculine) time.
2Th 2:7 For
the mystery (μυστήριον neuter singular) of lawlessness (the esoteric teaching that the Christian who sins will not die) is already working (
inside the church, encouraging Christians to practise sin): only
restraining/holding back (κατέχων neuter singular) [Christ's appearing] until
he (the man of sin) or
it (the mystery of lawlessness) becomes out of the midst (of the church).
2Th 2:8 And then shall
that wicked person (ὁ ἄνομος masculine singular) be revealed,
whom (ὃν masculine singular) the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
2Th 2:9 Even him,
whose (οὗ masculine singular) coming is after the working of Satan with all power and signs and lying wonders,
So, IMHO there are two
things restraining.
1. The delay of the apostasy/falling away is restraining the revelation of the Lord (v. 3 and 6).
And 2. the mystery of lawlessness at work in the church is the seed that will eventually become a great apostasy within the church. But this mystery of lawlessness is only restraining/delaying Christ's appearing, by making the church less effective in winning the number of souls God is aiming for for His family; but this mystery of lawlessness will not prevent Christ's return. And this mystery of lawlessness will stop restraining Christ's return when the son of perdition comes out of the midst of the fully leavened church I think the translation of v. 7 should be "until he (the wicked one) becomes out of the midst of the church", rather than until it (the mystery of lawlessness) comes out of the church, because the mystery of lawlessness remains in the church at the revelation of the wicked one and leads to the great apostasy of those in churches who will follow the antichrist.
The Lord will not return until the world is evangelised with the true gospel (not the mystery of lawlessness) and the full number of the nations is come in. he will also not return until after the son of perdition is revealed whom he will slay with the sword of His mouth.
So, the mystery of lawlessness inside the church is presently delaying Christ's return by hindering the churches evangelism of all nations, people and tongues. And the delay of the revelation of the son of perdition is delaying the Lord's return, because 1. he must be revealed so that Jesus can slay him at His coming, And 2. he must be revealed to offer the strong delusion that will draw all the false believers out of the church and produce the falling away that must come first.