Reference for Bava Metzia 144:3
יתיב מרימר וקאמר להא שמעתא אמר ליה רבינא למרימר אלא הא דאמר ר' יוחנן גזירה שמא יגבה מזמן ראשון נימא לא ניתן ליכתב א"ל הכי השתא התם נהי דלא ניתן ליכתב מזמן ראשון אבל ניתן ליכתב מזמן שני הכא לא ניתן ליכתב כלל
It is a precautionary measure, lest he exact his debt as from the earlier date, — let us say that it was not permissible to write it at all! — Said he: Is there the least analogy? There, granted that it was not permissible to write it from the earlier date, it was permissible to write it from the later date; but here it was not permissible to write it at all. But surely with respect to that which has been taught: As to claims for land improvement,<span class="x" onmousemove="('comment',' V. supra 14b. ');"><sup>5</sup></span> e.g., if one took away unlawfully a field from his neighbour and sold it to another, who effected improvements therein, and then it was seized from him [by the first owner], when he [the buyer] exacts [his due from the robber], he may collect the principal [even] from mortgaged property [that has since been sold], but the improvements only from the free [i.e., unsold] property<span class="x" onmousemove="('comment',' He is empowered to collect the principal even from sold property in virtue of the deed of sale, which guarantees to indemnify the purchaser in the event of its being seized and mortgages the vendor's estates for that purpose. ');"><sup>6</sup></span>