^2:22 `Behold, I will cast her upon a bed of sickness, and those who commit adultery with her into great tribulation, unless they repent of her deeds.

'Behold, I will cast her upon a bed of sickness, and

The same bed "she", Jezebel, used for pleasures/immoralities has turned into a bed of sickness.

Symbolically, "Jezebel" is left among the church members to test if they will be true to the Lord or if they will commit spiritual fornication. You can tell this Jezebelian behavior when the church members are able to flirt with the Devil and enjoy his pleasures and yet remain "pious church members". However, so many of these pleasures soon become evident (even among "pious church members") such as alcoholism, AIDS, drugs, gluttony etc.

those who commit adultery with her into GREAT TRIBULATION unless

In James 4:1-10, we are warned that friendship with the world is hostility toward God. And the result of that friendship will be a great tribulation. It is not clear if this refers to the seven years of great tribulation (which such friendship certainly would win) or if this refers to individual tribulations of great magnitude such as family suffering, unresolved arguments, workplace clashes.

The key is

they REPENT of their DEEDS.

Even during the time of sickness in the first part of this verse, there still is time to repent. A great tribulation is guaranteed if subversion in the church is not

Repent ..... a recurring theme in Revelation!!!