When attending a royal banquet or any sort of special feast, one would probably not want to get drunk. However, we see Yoseph’s brothers doing exactly that (Gen. 43.34): “וַיִּשְׁתּ֥וּ וַֽיִּשְׁכְּר֖וּ עִמּֽוֹ and they drank and got drunk with him.”
Sure, they are all together, but they don’t know that Yoseph is their brother, nor are they celebrating anything in particular, so what reason is there for them to be drinking so why are Yoseph’s brothers drinking so much that they get drunk at that meal?
One thing to notice is that this story stands out, since we’ve only seen one person as being described as getting drunk in the Torah – Noah (Gen. 9.21). Furthermore, there are no other stories in the Torah describing people getting drunk (the lone exception to any further reference of getting drunk is a poetic description (Deut. 32.42)), making this scene stand out even further.
Rabbi Ovadiah ben Jacob Sforno (1475-1550) explains the brothers’ drunkenness as arising from having been given really fine wine (ספורנו): “במיני יין מלכות רב שנתן לפניהם שלא היו מורגלים בהם they were being served the kind of royal wines, to which they were not accustomed.” This 16th century Italian rabbi probably knew a great deal about wine, since many fine wines come out of that area. And anyone who has ever been served or consumed any beverage that is significantly of a higher quality than one typically drinks can be so utterly fascinated and taken with it that they keep consuming more and more of it, almost simply out of fascination. Whether that beverage is wine, whiskey, beer, or anything else, one can easily slip into consuming much more than they might typically consume of that beverage.
This understanding of the brothers’ significant consumption of the royal wine may also connect us to Noah’s drunkenness. Just as Noah would have been surprised by the effects of wine, having never drunk it before, causing him to be surprised and totally overtaken by the effects that it had on him, here, too, the brothers are being overtaken and surprised by the incredible quality of this wine and what it does to them.
So, it’s not so much that Yoseph’s brothers were celebrating anything or in a particularly celebratory mood, it could just be that they were exposed to a much higher quality of wine than they had ever had and were overtaken and surprised by how good these royal wines were, causing them to get drunk.