Reference for Bava Kamma 178:4
וטעמא מאי כדי שלא תהא קלה בעיניו להוציאה הכא מגרש לה וגבי ליה בחבליה מינה אי הכי השתא נמי מגרש לה וגבי ליה בחבליה מינה
that it is prohibited for any man to keep his wife without a <i>kethubah</i> even for one hour, the reason being that it should not be an easy matter in the eyes of the husband to divorce a wife. So also here if the <i>kethubah</i> be assigned to him he might easily divorce her and have her <i>kethubah</i> for himself as compensation for the injury. But if so [even now that the <i>kethubah</i> remains with her] would he just the same not find it easy to divorce her, as he would retain the amount of her <i>kethubah</i> as compensation for the injury? [This however would not be so where] e.g., the amount of her <i>kethubah</i> was much more than that of the compensation as on account of the small amount of the compensation he would surely not risk losing more.<span class="x" onmousemove="('comment',' [I.e., the difference between the large amount of the kethubah and the amount due to him as compensation.] ');"><sup>4</sup></span>