Double of what?

Surely this does not mean double blessing for all her sins. Likewise it can’t be double punishment for all her sins. I wonder if it is more like double taxes for all her sins—as if there is a tax we are required to pay (think of it like tithing) which doesn’t pay for the cost of our salvation but represents a buying into the process—and for sinning against the covenant Jerusalem was required to pay double as a fine for transferring a heater light (not that double was enough to pay for either the initial salvation or the sin, let alone both.

On the other hand, perhaps it is a double blessing. Blessed once because the Lord blesses His children—and especially those of the covenant—and blessed again in having her sins blotted out.