From: Rabbi Akiva Eiger
To: Rabbi Hirsch Bleichrodt
Rabbi Akiva Eiger addresses why ein shaliach lidvar aveirah does not invalidate the agency for delivering a bill of manumission, suggesting the Mishnah refers to cases where emancipation fulfills an obligation rather than violating the aseh of l'olam bahem ta'avodu. The teshuvah then explores the broader definition of bar chiyuva in the context of ein shaliach lidvar aveirah, raising a doubt whether prohibited emancipation takes effect at all under the principle of ai avid lo mehani.
Source: Shu"t Rabbi Akiva Eiger §194