During Passover meal there were four cups of wine. The fourth cup was the cup of consummation that would complete the Passover. When the third cup was drank when Jesus declared, this is my body and this is my blood Jesus went to the garden skipping the fourth cup of wine of passover. In the garden Jesus said “Let this cup pass from me, though not my will but yours be done”. Jesus was about to seal the new covenant as the Kingdom would come as He is lifted up on the cross. The cup is tied into the Passover. It was the fourth cup or cup of consummation of the Passover. After His suffering when He was on the cross He said, “to fulfill what has been written I thirst.” Hyssop was then dipped into a bowl of wine and given to Jesus. After He drank it He said “it is finished” bringing the Passover to it’s consummation as He establishes the new covenant. This is the cup. It is the cup of consummation at Passover as the lamb of God takes away the sin of the world not the cup of God’s wrath.
It is true that the cup that Jesus drank was not the cup of God’s wrath. Rather it was the cup of suffering which Jesus underwent for our sakes.
It was the fourth cup of the Passover meal where Jesus established the new covenant. The slayed lamb began in the room of the Passover and ended on the cross when Jesus said “It is finished” after drinking the wine. The fourth cup of the Passover was the cup of consummation. It was this cup that Jesus said in the garden, “Let this cup pass from me”. He said this after the third cup of Passover was drank. Passover had four cups. The fourth was the cup of consummation - It is finished. The Eucharist was thus established. When Jesus asks, “Are you able to drink my cup?” He’s referring to eating His flesh and drinking His blood. This was a hard teaching that caused many to turn away from Him. It is the cup of salvation. The kingdom is in our midst in the Holy Eucharist as we receive heaven.
I read all of that in your initial post. What is your source?
It comes from the text of scripture. Listen here as Dr. Scott Hahn takes you through the Bible establishing that the cup is directly linked to the Fourth Cup of Passover