Charles Spurgeon Commentary 2 Thessalonians 2:5-7

"Remember ye not, that, when I was yet with you, I told you these things? And now ye know that which restraineth, to the end that he may be revealed in his own season. For the mystery of lawlessness doth already work: only [there is] one that restraineth now, until he be taken out of the way." — 2 Thessalonians 2:5-7 (ASV)

Do you not remember that, when I was yet with you, I told you these things? And now you know what withholds, that he might be revealed in his time. For the mystery of iniquity does already work:

There were certain reasons why that gigantic iniquity should begin to be developed even while the Roman Empire was in power to keep it in check; and when that passed away, there was the opportunity for "the mystery of iniquity" to become the despot of the world.

Remember ye not, that, when I was yet with you, I told you these things? And now ye know what withholdeth that he might be revealed in his time. For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.

There was something that hindered the full development of Antichrist in Paul's day. When that was taken out of the way, then there would be a fuller revelation of this sinful system.