Date: 17 Shevat 5595
From: Rabbi Moshe Sofer
To: Rabbi David
The responsum discusses whether the wife of the 'mekoshesh' (the man who gathered wood on Shabbat) was subject to yibum, considering the halachic status of a public Sabbath desecrator as an apostate.
Source: Shu"t Chasam Sofer Collected §54