Reference for Shabbat 226:12
(ישעיהו י, טז) ותחת כבודו יקד יקוד כיקוד אש א"ר יוחנן ותחת כבודו ולא כבודו ממש ר' יוחנן לטעמיה דר' יוחנן קרי למאניה מכבדותי
R. Eleazar said: Hence [it may be deduced] that vinegar is beneficial in hot weather. R. Samuel b. Nahmani said: He intimated to her, A son is destined to come forth from thee whose actions shall be as sharp<span class="x" onmousemove="('comment',' Lit., 'hard', 'grievous'. ');"><sup>42</sup></span> as vinegar; and who was it, Manasseh — And she sat beside the reapers.<span class="x" onmousemove="('comment',' Ibid. ');"><sup>43</sup></span> R — Eleazar observed: At the side of the reapers, but not in the midst of the reapers: he [Boaz] intimated to her<span class="x" onmousemove="('comment',' By seating her thus. ');"><sup>44</sup></span> that the Kingdom of the House of David was destined to be divided.<span class="x" onmousemove="('comment',' Just as the reapers made a division between her and him. ');"><sup>45</sup></span>