23.2.f,g
DH In veha'Tanya Ma'aseh b'Echad
https://dafyomi.co.il/nedarim/tosfos/nd-ts-023.htm#:~:text=%D7%95%D7%90%22%D7%AA%20%D7%95%D7%9E%D7%90%D7%99%20%D7%A9%D7%A0%D7%90,from%20his%20property%3B
On 23a, the ran seems to indicate that the host makes the neder, but the original case is very clear that it's the guest making the neder.
Why does the Ran confuse the matter?
Paul Davidowitz, Long Beach, NY, USA
The Mishnah (end of 23a) states that Rebbi Eliezer ben Yakov said what the host can do if he wants his friend to eat in his house. The Ran (DH Piska) explains that he makes all of his property forbidden to his friend if his friend does not agree to eat in his house. So it is the host who is making the Neder in the original case.
Kol Tuv,
Dovid Bloom