Reference for Yevamot 33:13
<big><strong>גמ׳</strong></big> אמר רב נחמן מאן דתני ראשונה לא משתבש מאן דתני שניה לא משתבש מאן דתני
AS HER RIVAL. IF HE<span class="x" onmousemove="('comment',' The second brother. ');"><sup>47</sup></span> ADDRESSED TO HER A MA'AMAR<span class="x" onmousemove="('comment',' I.e., said to her in the presence of witnesses, 'Be thou betrothed unto me'. ');"><sup>48</sup></span> AND DIED,<span class="x" onmousemove="('comment',' Prior to the consummation of the marriage. ');"><sup>49</sup></span> THE SECOND,<span class="x" onmousemove="('comment',' V. note 7. ');"><sup>50</sup></span> MUST PERFORM <i>HALIZAH</i><span class="x" onmousemove="('comment',' With the third brother. Since her husband's union with his deceased brother's widow was not consummated he never was her legal husband, and as she is consequently not her rival she cannot be exempt from the halizah. ');"><sup>51</sup></span> BUT MAY NOT ENTER INTO THE LEVIRATE MARRIAGE.<span class="x" onmousemove="('comment',' Because the ma'amar that the husband of the second addressed to the first widow has partially attached that woman to him, and the second has, in consequence, become the partial rival of a forbidden relative and is, therefore, Rabbinically forbidden to enter into the levirate marriage. ');"><sup>52</sup></span> <b><i>GEMARA</i></b>. R. Nahman said: He who uses the expression FIRST<span class="x" onmousemove="('comment',' In describing the widow of the first deceased brother. ');"><sup>53</sup></span> commits no error and he who uses the expression SECOND<span class="x" onmousemove="('comment',' In describing the widow of the first deceased brother. ');"><sup>53</sup></span> also commits no error. 'He who uses the expression