Reference for Bava Batra 320:15
וניחוש דלמא זייף וכתב מאי דבעי וחתימי סהדי
[The fact], however, [is that the law of] a folded [deed] is [only] Rabbinical, and the Scriptural verses [quoted] are a mere <i>asmakta</i>.<span class="x" onmousemove="('comment',' [H] 'support', i.e., the Scriptural text was used by the Rabbis as some slight support, or mnemotechnical aid to the laws of the plain and folded deeds which they themselves have enacted. ');"><sup>36</sup></span> What is the reason why the Rabbis instituted a folded [deed]? — They were [in] a place [inhabited] by priests, who were very hot-tempered and they divorced their wives.<span class="x" onmousemove="('comment',' For the slightest or imaginary provocation. A plain bill of divorce was easily obtainable, and once the divorce had taken place none could re-marry his wife, since a divorced woman is forbidden to a priest. Cf. Lev. XXI, 7. ');"><sup>37</sup></span> Consequently the Rabbis made [this] provision,<span class="x" onmousemove="('comment',' The folded bill of divorce. ');"><sup>38</sup></span>