After Yosef had revealed himself to his brothers, he gave them each three חליפות שמלות, changes of clothing. But to his brother, Binyamin, he gave five חליפות שמלות.
The Rabbis questioned if this was really a wise thing to do. After all, the trouble began between Yosef and his brothers because they were jealous of Yosef’s favored status in the family. And now Yosef is doing this again.
There are two answers to this question. The first is that Yosef was testing the brothers to see if they got over this pettiness of comparing who gets what. Their acceptance of Yosef’s action was a positive step forward.
The second answer was that the five garments Binyamin was given were a רמז, hint, to the five royal garments Mordechai, a descendant of Binyamin, wore in the Purim story after Haman was killed and Mordecha took his position.