Related על קידושין 38:21

"[Be betrothed to me] with the understanding that if I die you will not bound to a levir"—she is betrothed but his stipulation is invalid, for he stipulated against what was written in the Torah, and anyone who stipulates against what is written in the Torah, his stipulation is invalid. "With the understanding that I will have no responsibility for you for clothing or sex"—she is betrothed but his stipulation is invalid. This is the pneumonic: Anyone who stipulates against what is written in the Torah regarding a monetary matter—his stipulation stands; with a non-monetary matter—his stipulation is invalid.