Reference for Yevamot 209:4
ולר"ע מאי שנא רקיקה ומאי שנא קרייה
[that the validity refers to her state of prohibition] to the brothers.<span class="x" onmousemove="('comment',' The second meaning of vkuxp (v. supra note 4. (b) being that the woman is forbidden to contract the levirate marriage with any of the brothers. Cf. Git. 24b. ');"><sup>9</sup></span> Thus you have our contention proved. According to R. Akiba, wherein lies the legal difference between the act of spitting and that of reciting?<span class="x" onmousemove="('comment',' Since both acts are not indispensable, why does the former act according to R. Akiba cause the sister-in-law to be forbidden to the brothers (as has just been proved), while the latter does not (R. Akiba having stated supra that there was 'no reason whatsoever for apprehension')? ');"><sup>10</sup></span>