With this biblical quotation, Uncle Jack is signifying that Atticus is a Christ-like figure. He is also making a plea that Atticus figuratively get down from his cross and not represent Tom Robinson at the upcoming trial. Like Jesus, Atticus knows he must do the morally right thing, even if it means taking great personal risks. The biblical line from Matthew 26:39 refers to Jesus asking that he not be made to suffer for the sins of others. However, Jesus still dies on the cross to do what he feels is right. In this sense, "let this cup pass" means to escape a terrible event. Uncle Jack realizes that Atticus is in a similar situation but urges him to choose his personal safety over his moral crusade.

Atticus responds to Uncle Jack by saying that he couldn't face his children if he refused to be Tom Robinson's attorney. He is certain that the case is lost already due to what he calls "Maycomb's usual disease" (racism). He knows that this case will come down to the word of a black man against the word of the Ewells. With the deep-seated racial prejudices of Maycomb, Atticus predicts that his case will end in a guilty verdict. In fact, the reader learns in this scene that Atticus did not choose to represent Tom Robinson. It was Judge John Taylor who appointed him. Atticus would rather he was not chosen. However, once selected to represent Tom Robinson, Atticus does not feel like he can "let this cup pass" and forgo his duty to attempt to do what he knows is the right thing to do.

Uncle Jack is alluding to the Biblical account of Jesus’s prayers before his crucifixion when he asks Atticus if he is going to allow this cup pass from him in chapter nine. In the Gospel of Matthew, Jesus prays for God to allow this cup to pass from him before he is crucified. Jesus is essentially asking God to prevent him from being crucified and save him from suffering a brutal death. The figurative cup Jesus is speaking about symbolically represents an arduous, painful task that is necessary to complete for the well-being of others. By figuratively accepting the cup, Jesus is willing to sacrifice his life for the salvation of humanity.

Uncle Jack recognizes that Atticus will suffer at the hands of his racist neighbors for defending a black man and Atticus's decision to represent Tom Robinson will cause him a significant amount of stress. Similar to the way Jesus petitioned God to intervene and save him from his harrowing experience, Atticus also has the opportunity to step away from the case and figuratively allow the cup to pass from him. By refusing to defend Tom Robinson, Atticus will save himself a significant amount of anxiety and please his prejudiced neighbors. Despite the pressure, pain, and stress attached to defending a black man in Maycomb, Atticus demonstrates integrity and courage by following through with the difficult task, which is similar to the choice made by Jesus to become a martyr.

In Chapter 9 of Harper Lee's To Kill a Mockingbird, Uncle Jack is creating a biblical allusion when he says to Atticus, "Let this cup pass from you, eh?"

We read in the gospels of Matthew, Mark, and Luke that just after Jesus's last Seder, a feast that marks the start of Passover, just prior to his crucifixion, Jesus leads a few of his disciples to the Garden of Gethsemane to pray. While praying, Jesus asks God the Father, "My father, if it is possible, let this cup pass from Me; yet not as I will, but as You will" (Matt 26:39; Mrk 14:36; Lk 22:42). Shortly after praying, Jesus is betrayed by Judas and arrested by the Romans. During a Seder, drinking from a cup of wine has symbolic meaning. Four toasts are made to God from four cups of wine in celebration of God's four expressions of redemption. Hence, when Jesus asks God, "Let this cup pass from me," he is metaphorically asking to be permitted not to drink a toast from the particular cup he is metaphorically being handed in celebration of redemption because he does not want to do the deed that will lead to that redemption. In other words, Jesus knows God's people will be redeemed through his upcoming death, and he is asking to be permitted to escape that death. The phrase "let this cup pass" has become a euphemism to mean "let me escape this horrible event," but for Jesus, the "cup," or horrible event, is specifically tied to the salvation of God's people.

In To Kill a Mockingbird, Uncle Jack uses the words "let this cup pass" to mean something similar to Jesus's own words. Atticus had just explained that Tom Robinson's case is hopeless because the evidence consists of nothing but Robinson's words against the Ewells'. Yet, Atticus hopes to at least "jar the jury a bit" and appeal to the higher courts. He further confides that he had "hoped to get through life without a case of this kind," meaning that he had hoped to escape having to suffer through trying to defend an innocent African-American man before a racially prejudiced jury. He knows that in doing so, he is offering himself up as a great sacrifice to society because, even though he is acting to try and preserve the life of an innocent man, society's prejudiced members will metaphorically tear Atticus and his children to bits through their ridicule. Uncle Jack follows Atticus's comment that he had hoped to avoid a case like this with his question, "Let this cup pass from you, eh?" In so doing, Uncle Jack is implying he understands Atticus is making a painful sacrifice that, like Jesus, he would prefer to avoid. Yet, Atticus knows he must go through with his defense of Robinson because, like Jesus, Atticus understands sacrificing himself is the only morally correct thing to do.