The Cup of Blessing that Paul mentions in
1 Corinthians 10:16 refers to the Third Cup drank at every seder. It's not a figurative cup.
Matt. 26:29; Mark 14:25 – Jesus is celebrating the Passover seder meal with the apostles which requires them to drink four cups of wine. But Jesus only presents the first three cups. He stops at the Third Cup (called “Cup of Blessing” – that is why Paul in 1 Cor. 10:16 uses the phrase “Cup of Blessing” to refer to the Eucharist – he ties the seder meal to the Eucharistic sacrifice). But Jesus conspicuously tells his apostles that He is omitting the Fourth Cup called the “Cup of Consummation.” The Gospel writers point this critical omission of the seder meal out to us to demonstrate that the
Eucharistic sacrifice and the sacrifice on the cross are one and the same sacrifice, and the sacrifice would not be completed until Jesus drank the Fourth Cup on the cross.
Matt. 26:30; Mark 14:26 – they sung the great Hallel, which traditionally followed the Third Cup of the seder meal, but did not drink the Fourth Cup of Consummation. The Passover sacrifice had begun, but was not yet finished. It continued in the Garden of Gethsemane and was consummated on the cross.
If the Third Cup
1 Corinthians 10:16 is figurative, then His death on the cross is also figurative. That's Gnosticism, not Christianity.