From: Rabbi Moshe Sofer, Frankfurt am Main
To: Unknown recipient
The responsum discusses the prohibition of nullifying chametz on Shabbat, citing Tosafot and other Rishonim, and also addresses the immersion of vessels on Shabbat and Yom Tov, explaining the reasoning behind the prohibition based on 'makom' and 'shema yisheha'.
Source: Shu"t Chasam Sofer Collected §33