The gemora brings the teachings of Rav Huna in the name of Rav: there is a difference between she'Lo Ochal Kikar Zo and Kikar Zo Alai.
My question is can we apply to this, the concept of Mitzos Lav le'Henos Nitnu and he will be able to use the bread even if he said Kikar Zo Alai? Or since the eiruv is voluntary he only uses the eiruv because he wants to go to Techum Shabbos which in itself is not a mitzvah then it is called a Hana'ah.
Thank you
Kesivah v'Chasimah Tovah
Nachmen, Boruch She-Kivanta! Your question is asked by Tosfos here. Tosfos writes that this question applies if one maintains both the opinion that one can only make an eruv for a matter of a Mitzvah (as the Gemara below 31a states) and one also maintains that Mitzvos Lav le'Heinos Nitnu (there is an opinion which disagrees and maintains that Mitzvos le'Heinos Nitnu).
Tosfos answers in the name of Rashbam that according to these opinions Rav Huna is telling us that if he said "Konam eating kikar zo alai" he may not eat it because a konam is similar to hekdesh and if one permitted this one may come to permit hekdesh as an eruv.
Kesivah vaChasimah Tovah
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