[Avodah] violating a lav to perform a mitzva

[Jacob Farkas]

Rt. Chana Luntz wrote:
> I find myself constantly finding examples where I end up saying  - but 
> isn't this another case where there seems to be an assumption that if we 
> are doche a Torah mizvah, a rabbinic mizvah kama v'kama, but anyway - 
> you are more than welcome to join me on my hunt.

The Qal Vahomer is not valid because Hakhamim Asu Hizuq Lidivreihem 
Yoser Mishel Torah. It is therefore possible to apply dehiya for a 
D'Oraisa, but not for a D'Rabbanan.

--Jacob Farkas