וַיִּשָּׂ֨א מַשְׂאֹ֜ת מֵאֵ֣ת פָּנָיו֮ אֲלֵהֶם֒ וַתֵּ֜רֶב מַשְׂאַ֧ת בִּנְיָמִ֛ן מִמַּשְׂאֹ֥ת כֻּלָּ֖ם חָמֵ֣שׁ יָד֑וֹת וַיִּשְׁתּ֥וּ וַֽיִּשְׁכְּר֖וּ עִמּֽוֹ׃
И были взяты им части до него; но Вениамин'Их доля была в пять раз больше, чем у них. И они пили и веселились с ним.
Rashbam
ותרב, as if the Torah had written ותרבה. The meaning is that Binyamin’s gift from Joseph was far greater than the gift received by his brothers. A parallel construction to the word vaterev appears in connection with the construction of the Tabernacle ותכל, vatechel, where it means that the construction had been completed (Exodus 39,32).
Radak
וישא, the person who handed out the gifts. We find a similar construction where the subject is presumed without being named or being specifically referred to in 48,2 when Yaakov is informed that Joseph is about to visit him. The Torah there also uses the impersonal ויגד, “someone told,” without bothering to inform the reader who it was that informed Yaakov. All this friendliness which Joseph displayed during the meal was intended to contrast with the manner in which they, the brothers would do everything in their power to cause him anguish and discomfort prior to the time when they had sold him. He displayed especial fondness for Binyamin because he had been forced to come to Egypt on account of what must have seemed like his caprice, and to compensate him for having been separated from his father for no apparent reason. At least, these were some of the thoughts which the brothers thought of to explain Joseph’s strange behaviour.