There has long been debate about which rabbinic text is dependent upon which. It is very rare that we know certainly the date of the texts or when one is clearly citing or building its own interpretation upon that of another text. This is certainly true of TgRuth. I am just re-reading Derek Beattie’s, “Towards Dating the Targum of Ruth,” in Word in Season, (Sheffield, England Ithaca, NY: Snow Lion Publications JSOT Pr), 1986. On page 216 he has this phenomenal little quote regarding parallels that is worth sharing.
As I recall from schoolboy geometry, the essence of parallels lies in their never meeting and, certainly, Tg. Ruth never seems to actually make contact with any of its many parallels in talmud and midrash.
True, this is a bit apples and oranges, but it is worth reminding ourselves that two thoughtful and learned people when confronted with the same biblical text may well come to very similar interpretations. One need not be dependent or in response to the other.
The example in question is Ruth 3:8 and the interpretation of הָאִישׁ וַיִּלָּפֵת. TgRuth renders it גברא ורתת ואיתרכיך בישׂריה כליפתא מן רתיתא, “the man was startled, and he trembled, and his flesh became soft like a turnip from fear.” The Talmudic text is b San. 19b. “What is the meaning of וַיִּלָּפֵת? Rab said: His flesh became [as hard] as turnip heads.” Rashi makes it explicit for us by saying “his member became hard.” BUT nonetheless, we are told, he resisted his desires. (Don’t want to mislead you as to the point of the story and its interpretation!)
Beattie points out that while both share their reading of the Hebrew as being derived from לפת, “turnip” (instead of “trembling”), but they go in different directions. The Targumist likes his turnips boiled (“his flesh was soft like a turnip”) while Rab’s turnip is raw and hard. So there you go. They start at the same place and have similar readings and yet they are different. Are they dependent or reacting one to another? I think not. They are simply reading the Hebrew in the same way and there are only so many exegetical conclusions they can arrive at from that starting point.