Reference for Yevamot 211:4
ומעשה באשה אחת שנפלה לפני יבם שאין הגון לה ואמרו לו חלוץ לה על מנת שתתן לך מאתים זוז ובא מעשה לפני רבי חייא והכשירה
When a levir is told, 'Submit to her <i>halizah</i> on the condition that she gives you two hundred zuz'.<span class="x" onmousemove="('comment',' V. Glos. Even if the promised sum was not forthcoming, the halizah is valid. Any condition in connection with an act which, like halizah. cannot be performed through an agent is illegal and void. Cf. Keth. 74a. ');"><sup>10</sup></span> So it was also taught [elsewhere]: A <i>halizah</i> under a false assumption is valid; and what is meant by a <i>halizah</i> under a false assumption? One in which the levir is told 'Submit to her <i>halizah</i> on condition that she gives you two hundred zuz'. Such an incident, in fact, occurred with a woman who fell to the lot of an unworthy levir who was told, 'Submit to her <i>halizah</i> on condition that she gives you two hundred zuz'. When this case came before R. Hiyya he ruled that the <i>halizah</i> was valid. A woman<span class="x" onmousemove="('comment',' A sister-in-law who fell to the lot of an undesirable levir. (V. infra). ');"><sup>11</sup></span>