Wiktionary
a. (context simile English) extremely pure; totally pure (typically "pure" in the sense of "virtuous").
Usage examples of "pure as the driven snow".
In the good old days, it was just naturally assumed that all the active participants were pure as the driven snow.
The deal I have in mind calls for you remaining as pure as the driven snow.
She had to be pure as the driven snow-she couldn't violate the Holy Covenant now even if she were willing to accept the consequences.
I will say this and then no more: my wife was as pure as the driven snow when she came to me on our wedding night, but I never would have believed it from her behavior up until that point.
But I must ask you to keep secret the fact that two hundred and one wasn't pure as the driven snow.
It was up to the ladies to say whether they'd been pure as the driven snow or had taken it all three ways more than once.
This is an uncommonly dirty world and I automatically suspect those as pure as the driven snow.