There is a syntactical irregularity in the verse that records this exchange: "And Joseph's brothers saw that their father had died, and they said, 'Lest (lu) Joseph will hate us and repay us all of the evil that we have done him.' And they sent to Joseph saying, 'Your father commanded before his death...'" (Genesis 50:15-16).
The medieval commentator Rashi notes that elsewhere in the Bible, the word "lu" always means either "if only" or "perhaps." Here, though, "lu" must mean "lest." Otherwise, the verse would read, "If only Joseph would hate us," and surely Joseph's brothers do not want him to hate them. They go to great lengths to convince Joseph that their father had asked for forgiveness for them.
An alternate reading of the verses, though, could suggest that the brothers are feeling conflicted. Certainly, a part of them wants good treatment and absolution from Joseph. I would argue, though, that another part of them wants Joseph to hate them. In order to understand how this could be, we must look back at the history of the relationship between Joseph and his brothers.
In Chapter 37, overcome by jealousy and rage, the brothers throw Joseph into a pit and sell him as a slave. The brothers return home to face their father's tormented anguish over the loss of Joseph, and for 22 years they walk around with a crippling burden of guilt.
Their abuse of Joseph weighs heavily on them, and they interpreted even apparently unrelated events through the lens of their culpability. When the viceroy of Egypt--a disguised Joseph--treats them harshly and accuses them of spying, the brothers begin to talk about their home life and about the brother who is missing.
