And He went a little beyond [them,] and fell on His face and prayed,
saying, "My Father, if it is possible, let this cup pass from Me;
yet not as I will, but as Thou will.
~ Matthew 26:39
We have come to understand the expression Christ uses when He says “cup” refers to the wrath of God that He will endure. We find elsewhere in scripture that when one has a cup it shows ownership. The owner is ultimately responsible for the contents of the cup, and usually the contents are not pleasant.
For example, in Ezekiel 23:31-33 we read,
'You have walked in the way of your sister; therefore I will give her cup into your hand.' Thus says the Lord GOD, 'You will drink your sister's cup, which is deep and wide. You will be laughed at and held in derision; it contains much. You will be filled with drunkenness and sorrow, the cup of horror and desolation, the cup of your sister Samaria.'
Again in Psalm 11:6,
Let him rain coals on the wicked; fire and sulfur and a scorching wind shall be the portion of their cup.
Perhaps we find the origins of this in Genesis 44:1-17:
Then he commanded the steward of his house, “Fill the men's sacks with food, as much as they can carry, and put each man's money in the mouth of his sack, and put my cup, the silver cup, in the mouth of the sack of the youngest, with his money for the grain.” And he did as Joseph told him.
As soon as the morning was light, the men were sent away with their donkeys. They had gone only a short distance from the city.
Now Joseph said to his steward, “Up, follow after the men, and when you overtake them, say to them, ‘Why have you repaid evil for good? Is it not from this that my lord drinks, and by this that he practices divination? You have done evil in doing this.’”
When he overtook them, he spoke to them these words. They said to him, “Why does my lord speak such words as these? Far be it from your servants to do such a thing! Behold, the money that we found in the mouths of our sacks we brought back to you from the land of Canaan. How then could we steal silver or gold from your lord's house? Whichever of your servants is found with it shall die, and we also will be my lord's servants.”
He said, “Let it be as you say: he who is found with it shall be my servant, and the rest of you shall be innocent.” Then each man quickly lowered his sack to the ground, and each man opened his sack. And he searched, beginning with the eldest and ending with the youngest.
And the cup was found in Benjamin's sack. Then they tore their clothes, and every man loaded his donkey, and they returned to the city.
When Judah and his brothers came to Joseph's house, he was still there. They fell before him to the ground. Joseph said to them, “What deed is this that you have done? Do you not know that a man like me can indeed practice divination?”
And Judah said, “What shall we say to my lord? What shall we speak? Or how can we clear ourselves? God has found out the guilt of your servants; behold, we are my lord's servants, both we and he also in whose hand the cup has been found.” But he said, “Far be it from me that I should do so! Only the man in whose hand the cup was found shall be my servant. But as for you, go up in peace to your father.”
In this reading we find that the cup was given to Benjamin. He was innocent of the sin of his brothers against Joseph, yet Joseph chose him to bear the cup. When the brothers returned to Egypt, Judah pleaded with Joseph that they all should suffer together. But Joseph replies that only the one who has the cup will suffer. And what of the rest? They may "go to their father in peace".
Is that not what Christ has done for us? The innocent one bore the punishment of the cup while guilty sinners go to the father in peace.