Responsa for Bava Batra 294:5
אמר רבא אמר רב נחמן שכיב מרע שאמר ידור פלוני בבית זה יאכל פלוני פירות דקל זה לא אמר כלום עד שיאמר תנו בית זה לפלוני וידור בו תנו דקל זה לפלוני ויאכל פירותיו
unless he used the following expression:<span class="x" onmousemove="('comment',' Lit., 'until he would say'. ');"><sup>16</sup></span> 'Give this house to X that he may live in it', or 'Give this date-tree to X that he may eat of its fruit'<span class="x" onmousemove="('comment',' By transferring the possession of the concrete object. the abstract or the yet non-existing. may also simultaneously he transferred. ');"><sup>17</sup></span> Does this mean to imply<span class="x" onmousemove="('comment',' Lit., 'to say'. ');"><sup>18</sup></span> that R. Nahman holds the opinion that [only] the rights<span class="x" onmousemove="('comment',' Lit., 'thing'. ');"><sup>19</sup></span>
Teshuvot Maharam
A. A dowry gift becomes the property of the donee only if the marriage takes place. Therefore, neither A nor his daughter has ever gained title to B's money, and A must return the principal plus the interest to B. Even if B expressly stipulated that he will forfeit the 15 pounds if the marriage does not take place, such a stipulation is considered an Asmakhta and is not valid. B, however, must pay A for his trouble in managing B's investments.
SOURCES: Cr. 86; Pr. 285; Mord. B.B. 615; Agudah B.B. 198.