The goblet of the wise
הלוא אשר ישתה אדני בו והוא נחש ינחש בו וגו’
Is [this goblet] not that which my Master drinks from? He also divines with it…
Yosef, as the viceroy of Egypt, had his brothers fooled. They didn’t recognize him as their brother, and he sent them home without a clue. More than that, Yosef had a plan to set up his brother Binyamin. Yosef had someone plant his precious goblet in Binyamin’s bag. As the brothers journeyed home, they were arrested for theft. What was Yosef’s purpose for this whole ruse?
The simplest explanation would seem to be that Yosef was concerned. His brothers sold him as a slave, seemingly because of their jealousy. Perhaps it was because he was the son of Rochel, Yaakov’s favorite wife. Binyomin was Rochel’s other child. Yosef wasn’t sure if his brothers harbored a general hatred of Rochel’s children, and for all he knew Binyomin was a target of their animosity. Maybe they would sell him as a slave as well, when the chance would arrive.
Therefore, Yosef devised a plan to arrest Binyomin on false charges, and see if his brothers would come to Binyomin’s defense. They did, and that’s when Yosef revealed himself. However, we could still inquire, why did Yosef specifically choose to create this conspiracy using his precious goblet? Was there some specific intent in mind?
Perhaps Yosef was very purposeful in choosing to scare his brothers with an accusation of stealing his precious goblet. Maybe he was trying to remind them of the time they sold him as a slave. Besides the incredible pain they inflicted on their brother, there was something they didn’t take into account. By separating Yaakov from his favorite son, Yosef, they were also causing the former tremendous grief. But there’s more to it than that.
Yaakov took great efforts to teach Yosef all the Torah knowledge that he knew. The Torah calls Yosef Yaakov’s בן זקונים. While it could mean that he was the son of Yaakov’s old age, a זקן also connotes someone filled with wisdom. בן זקונים would then also mean Yosef was Yaakov’s wise son. This is how we know that Yaakov taught Yosef all that he knew.
We have many sources that compare the Torah to wine. As well, we are taught that a teacher learns the most from their students. Students make their teachers wiser. We can then therefore compare a student to a cup, who provides a way for the teacher to drink the wine of Torah. First, the teacher pours the wine into the cup. Meaning, they teach their student the Torah that they know. Subsequently, the teacher drinks the wine, by attaining the wisdom gained from teaching the student.
This was the intention of Yosef placing the goblet in Binyamin’s bag. Yosef’s servants, as they carried out their arrest, declared that this was the goblet that Viceroy Yosef drank from. This hinted to them that they not only stole Yosef’s goblet, but they stole their brother Yosef from their father. Yaakov would pour wine into Yosef, his goblet, as it were, and then would drink the wisdom gained from him. By selling Yosef, they took away this give and take relationship Yaakov was benefiting from.
This could be the intention behind the Aramaic translation of בן זקונים. Targum Onkelos translates it as בר חכים, which could be read as a wise son. However, it seems like it’s causative verb. Meaning, Yosef is someone who makes others wise. This is referring to the wisdom that Yaakov gained by teaching everything he knew to Yosef.
Yosef had good intentions. He wanted his brothers to be completely atoned for selling him as a slave. While they had their justifications, Yosef felt they hadn’t thought the matter thoroughly through enough. They didn’t realize what they were doing to their father. Not only were they taking away his favorite son, which they surely realized and considered, but they were taking away Yaakov’s main source for wisdom. For that, they needed the hint of the goblet. Only then could they properly repent.
 Based on Be’er Yosef to Genesis 44:5
 Genesis loc. cit.
 See Ramban to Genesis 42:9
 Genesis 37:3
 Kiddushin 32b; Seder Olam Chapter 30; Toras Kohanim 19:32; Mishneh Torah Hilchos Talmud Torah 6:1
 Rashi, Ramban, and Targum Onkelos ad. loc. Bereishis Rabbah 84:8. See further for more on the Targum’s understanding. See also Ba’al HaTurim ad. loc.
 For example, see Proverbs 9:5, Avodah Zarah 35a, and Vayikra Rabbah 30:1
 Taanis 7a; Makkos 10a
 Loc. cit.
 Ramban ad. loc.
 See Ramban loc. cit. who says that Yaakov taught Yosef סתרי תורה. According to Chagigah 13a, סתרי תורה are only given over to a חכם חרשים, which ibid 14a explains is a student who makes their teacher wise
 See Be’er Yosef, who explains the double expression נחש ינחש in our verse in a similar vein