פּירוש אויף בראשית 49:23

וימררהו ורבו AND THEY EMBITTERED HIM — His brothers dealt bitterly with him; Potiphar and his wife dealt bitterly with him, putting him into the dungeon. וימררהו is the same metaphor as וימררו 'וגו in (Exodus 1:14) “They made their lives bitter (וימררו )” (Genesis Rabbah 98:19).

וימררוהו ורבו, “they embittered him and they quarreled. This was the result of the arrow tongued brothers hating him already.

וימררוהו ורבו, they threw him into jail,

ורבו means his brothers became his adversaries (literally, men of strife). This verb is not a Kal form meaning they strove (with him) for were it so it should have been punctuated וְרָבוּ (from the root ריב), as in (Numbers 20:13) “These are the waters of Meribah, where the children of Israel strove (רָבוּ)”. And even if its meaning were “shooting arrows” (from the root רבה) it would have been punctuated in exactly the same way. It really has a passive force like (Jeremiah 2:12) שֹׁׁמּוּ שמים “Be astonished, O ye heavens” which is as much as הושמו; and likewise (Job 24:24) “They are exalted (רֹמּוּ) for a little while” which has the same meaning as הורמו except that הורמו and הושמו mean they are made to be exalted and astonished by others, whilst שמו and רמו and רבו denote that the actions arise out of the persons themselves: they make themselves to be astonished, they are exalted of their own accord, רבו means they became men of strife. A similar form is (Isaiah 23:2) “Be still (דֹּמּוּ) ye inhabitants of the isle” where דמו has the same meaning as the Nipal of נִדְמוּ ,דום. In this sense does Onkelos also translate it: ונקמהו “and they avenged themselves on him”.