The key text about the Restrainer is 2 Thessalonians 2:6-8, which says, “And you know what restrains him now, so that in his time he will be revealed. For the mystery of lawlessness is already at work; only he who now restrains will do so until he is taken out of the way. Then that lawless one will be revealed whom the Lord will slay with the breath of His mouth and bring to an end by the appearance of His coming.”
Paul is apparently surprised that his own teaching on the end times had not stopped the Thessalonians from believing the false claim, so he rehearses that teaching. The man of lawlessness cannot be unveiled while what is restraining (Greek ‘to katechon’, neuter participle of ‘katechō’, ‘to prevent, hinder, restrain’) him now is at work. In verse 7 Paul refers to he who now restrains (Greek. ‘ho katechōn’, masculine participle of the same word). This implies that the restrainer is neuter, yet the personality is masculine, in other words the restrainer is the Holy Spirit, and He prevents the premature manifestation of the man of sin as the very embodiment of iniquity. At Pentecost, the Holy Spirit assumed a special relationship to the Church as its indweller, who would be there forever (John 14:16-17). And as Jesus said in John 16:7 that if Jesus doesn’t go away the Holy Spirit doesn’t come, likewise, at the end, if the Holy Spirit doesn’t go away the man of sin doesn’t come. In other words, as the Holy Spirit and the Church are forever bound to each other (the Church is sealed in Him – Ephesians 1:13-14), the restraint can only be lifted when the restrainer removes Himself, and thus the Church removes herself, which happens at the rapture. This would imply that the people who are saved between the rapture and the final hour will experience the Holy Spirit in a similar matter as the saints before Pentecost, i.e. on a personal basis and not as a collective unified body.