From: Rabbi Moshe Sofer
To: Rabbi Yisrael
The Chasam Sofer rules that because the tena'im rishonim used the formulation 'he obligated himself' (hischayev atzmo) to provide meals for six years, this constitutes a full binding self-obligation enforceable against the heirs — not merely a future-tense kinyan atan. He dismisses the Rambam's objection regarding non-fixed amounts, citing the Shach's contrary ruling and the special status of obligations made in the context of marriage negotiations.
Source: Shu"t Chasam Sofer EH I §135