הלכה על בבא מציעא 7:10

However, the previous Mishnah (Bava Metzia 7:10) contradicts this rule. This Mishnah teaches that a borrower may make a condition that he excused from payment in all situations. The reasoning for this Mishnah is that tenai shebemammon kayam, that stipulations in regard to financial matters are valid even if they contradict Torah law. One owns his money so he may waive his Torah given right to collect money or conversely is permitted to agree to obligate himself to pay money that the Torah does not require him to pay.