From: Rabbi Moshe Sofer
To: Rabbi Aharon Fulda
The Chasam Sofer resolves an apparent contradiction between Tosfos in Kesubos and Tosfos in Bava Kamma regarding R' Akiva's position on lokeh u'meshalem through three resolutions, including distinguishing bal tashchis (no lashes) from the specific prohibition of oso lo sachris. He further develops a novel ruling that all esnan obligations are limited to letzeis yedei shamayim since the entire esnan institution is a Scriptural novelty that should be applied minimally, and reconciles the Rema's apparently conflicting rulings in CM 208 and YD 230 via the Rosh's distinction between annullable and non-annullable prohibitions.
Source: Shu"t Chasam Sofer CM §27