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In Franz Kafka's The Metamorphosis, we can view the apples and the number three within the same context. Gregor is seen by some as a Christ-like figure.
The similarities to Christ can be seen in Gregor's attitudes towards his family. They are very much like Jesus's own people (and even Peter) who betray Christ though he is one of their own. The number three is closely related to Christ in the form of "the Father, Son and Holy Ghost." (The number three is very significant throughout the story of Christ in the Bible.) We also find a description of Gregor's death, very similar to the crucifixion of Christ:
He remembered his family with deep feelings of love...He remained in this state of empty and peaceful reflection until the tower clock struck three in the morning...Then without willing it, his head sank all the way down, and from his nostrils his last breath flowed weakly out.
In this excerpt, Gregor's love for his family is similar to Christ's plea to God to forgive those who were responsible for Jesus' death, "Father, forgive them for they know not what they do." (Luke 23:34) Gregor does not move until the clock strikes three: in the crucifixion story, Christ hangs on the cross for three hours, dying at three o'clock (known as the "ninth hour"). (Matthew 27:46-50)
As is the case in the story of the death of Jesus, we recall that he was nailed to the cross, with his arms stretched, one on either side of the wooden structure that held him. His side was pierced as was common during the days of crucifixion to see if the executed person was dead. Kafka describes this with regard to Gregor also:
Since [the cleaning woman] happened to be holding the long broom in her hand, she tried to tickle Gregor with it from the door. When that was quite unsuccessful, she became irritated and poked Gregor a little, and only when she had shoved him from his place without any resistance did she become attentive. When she quickly realized the true state of affairs, her eyes grew large and she whistled to herself.
There is another section of the book that describes the apple Gregor's father intentionally throws at him:
A weakly thrown apple grazed Gregor’s back but skidded off harmlessly. However, another thrown immediately after that one drove into Gregor’s back really hard. Gregor wanted to drag himself off, as if he could make the unexpected and incredible pain go away if he changed his position. But he felt as if he was nailed in place and lay stretched out completely confused in all his senses.
The "apple" has long been associated with the story of Adam and Eve, and in The Metamorphosis, it seems to symbolize original sin, which "nails" Gregor in place, a description similar to that of Christ—who was nailed to the cross to combat sin that had come into the world with the eating of the fruit in the Garden of Eden.