After the meal, Joseph sent the brothers off. Unbeknown to them, however, Joseph had instructed his servant to hide his silver goblet in Benjamin’s pack. Joseph sent his servant to pursue his brothers and the goblet was discovered. By framing Benjamin, Joseph was creating a situation where his brothers could atone for having sold him. When the brothers would put their own lives at risk to save Benjamin, it would be as if they were doing so to save Joseph; thus, they would “undo” their crime against Joseph by doing the exact opposite. The brothers returned to Joseph, who informed them that they were all free to return home except for Benjamin.
The Gift of Love
וְאֶת גְּבִיעִי גְּבִיעַ הַכֶּסֶף תָּשִׂים בְּפִי אַמְתַּחַת הַקָּטֹן וגו': (בראשית מד:ב)
[Joseph said,] “Put my goblet – the silver goblet – at the top of the pack of [Benjamin], the youngest one.” Genesis 44:2

Joseph knew that the Jewish people would be in exile for a long time, and that not all of them would possess the same level of Divine consciousness that enabled him to thrive in Egypt. Joseph therefore sought a way of protecting them from Egyptian depravity, ensuring that they would eventually leave Egypt and receive the Torah. Joseph realized that what they needed was a love for G‑d powerful enough to overcome the materialism of Egypt. Joseph’s silver goblet alludes to this love, for the word for “silver” (kesef) is related to the word for “yearning” (kisuf). Joseph further knew that not-yet-fully-righteous people cannot spark such a love by themselves, so he implanted this love in them by “implanting” it within Benjamin.1