Vayehi II: Biblical Parallelism
ורבו - כפל לשון של חצים שבפסוק כמו יסובו עלי(ו) רביו, חציו. ולכן הוא נדגש. אבל מגזרת מריבה יאמר אשר רבו בני ישראל. כמו מן קם קמו, מן שב שבו, כן יאמר מן הרב רב עם ישראל, רבו. ומדמה הפסוק לשון הרע של [אשת] פוטיפר לחצים כדכת' חץ שחוט לשונם מרמה דבר, וידרכו את לשונם קשתם שקר. ורבו מגזרת רבב כמו סבו מן סבב, צהלי ורוני מן רנן. רבו שיטרוט ב"ל:
One of the things that every beginning student of Tanakh learns is the importance of parallelism in Biblical poetry. Many verses are arranged according to a parallel structure (A, B), where the first part (A) essentially means the same thing as the second part (B). This then becomes an extremely powerful tool for deciphering difficult words in poetic passages, provided they are used in parallel with more common terms.
As we have seen before, Rashbam is among the pioneering voices developing these sorts of theories about biblical literature. He uses the term כפל לשון to describe this parallelism and uses it here to great effect. In Bereishit 49:23, Ya’akov says of Yosef: וַיְמָרֲרֻהוּ וָרֹבּוּ וַיִּשְׂטְמֻהוּ בַּעֲלֵי חִצִּים. The word וָרֹבּוּ here is obscure. The temptation is to see it as describing מריבה, some sort of tension or fight, such that Yosef’s adversaries—using their arrows—are described as dealing with him bitterly, fighting with him and resenting him. Rashbam notes that the dagesh in the bet votes against this reading, since the plural third person past tense of fighting would be vocalized וָרָבוּ. But what really forecloses this interpretation is the principle of כפל לשון. Once we realize that the first and second parts of this verse are parallel, we realize that וָרֹבּוּ is likely synonymous with בַּעֲלֵי חִצִּים. It thus must refer to shooting arrows, which then calls to mind Iyov 16:13, where we find the same root referring to archers surrounding their victim.This sort of lexical problem solving is at the heart of Rashbam’s work, and comments like this one show how effective it can be in elucidating peshat. [For other uses of the principle of כפל לשון, see his comments on Bereishit 20:13, 25:23, 49:5 and 49:9.]