What Goes Around Comes Around
Yoseph’s brothers did not take the goblet, yet when Binyamin was accused by Yoseph (before they knew who he really was), Yehuda said (Breisheet 44:16): “What shall we say to my master? What can we speak? How can we justify ourselves? God has found the iniquity of your servants”. 


According to Rashi, Yehuda was saying that: “We know that we have done no wrong, but it has come from God to bring this upon us. The Creditor has found an opportunity to collect his debt”.


Yehuda does not admit to any guilt concerning the goblet, only that God has found a way of punishing them for an old sin.


Even before the brothers knew who Yoseph was, the guilt for having sold Yoseph was still on their minds.


Yoseph’s actions- not revealing who he was right away, calling his brothers spies, putting their money back in their bags, putting the goblet in Binyamin’s bag etc which may seem strange- were all done in order to help the brothers do Teshuva and to receive full atonement. Only after a person has done full Teshuva and committed to not making the same mistake in the future can a person be fully forgiven. The fact that this time the brothers were not willing to endanger Binyamin the way that they had endangered him showed Yoseph that they had really regretted what they had done and that they really went through a complete Teshuva process.