Today on John Piper's Desiring God Blog a guest writer named Steven Lee wrote a post titled "The Cup Consumed for Us." The post is a brief reflection on Matthew 20:20-28 where the apostles James and John are asked by Jesus "Are you able to drink the cup that I am to drink?" Lee interprets this verse in the way many Calvinists do, claiming that this cup Jesus is going to drink is "the cup of God's wrath." But is this true? And wouldn't such a claim make nonsense of Our Lord's words? That's what I'll address in this post.
Here's the essence of what Lee had to say:
What do we make of Jesus’s unusual statement, “Are you able to drink the cup that I am to drink?”
Key passages in the Bible connect God’s wrath with the imagery of a cup. ... [Jeremiah 25:15; Isaiah 51:17; Revelation 14:9-10; Matthew 26:39] ...
This is the same cup Jesus asks his disciples about in Matthew 20. It’s the cup of God’s wrath, a cup that has accumulated the fury of God against sins of all types. . . .
There, at Golgotha, our Savior drained God’s cup of burning anger down to the dregs. God poured out his wrath, full strength, undiluted, onto his Son. Paul summarizes the meaning of this great event, “For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God” (2 Corinthians 5:21).
Jesus drank the cup of God’s wrath for us so that he could extend the cup of God’s fellowship to us. We don’t get wrath anymore — now we get God. We get the sweet, satisfying reality of his eternal fellowship in Jesus Christ, through the Holy Spirit.
This 'reflection' is a good example of how Protestants unwittingly fall for traditions of men and don't even realize it. For a first time reader, all this might sound nice and even biblical, but upon asking the right questions you will see that this reasoning is seriously flawed and even dangerous.
First of all, identifying the "cup" of Matthew 20:22-23 as the "cup of God's wrath" is bad exegesis. The text doesn't say anything about the cup being God's wrath, nor do we see this when the Evangelists describe the Crucifixion.  The Gospel writers say nothing about God pouring out his wrath, "full strength, undiluted, onto his Son." That's just desperation to find proof for a teaching that isn't really Biblical at all. And as I've said ad nauseam on my numerous blog posts addressing Penal Substitution, such statements by Calvinists are pure blasphemy against the Holy Trinity.
The desperation goes so far as to make 2 Corinthians 5:21 a favorite magical text of Protestantism that says everything without really saying it at all. In this case, Lee follows the Protestant tradition of men which interprets the "made sin" of 2 Corinthians 5:21 as Jesus being damned by the Father. But enough of 2 Corinthians, let me show further why Lee's Calvinist interpretation is so far off the mark.
Notice that in the original account when Jesus asks James and John if they can drink the cup, they respond in the affirmative, as Lee rightly notes. And Jesus responds to their affirmative by saying: "The cup that I drink you will drink, and with the baptism with which I am baptized, you will be baptized" (Mark 10:38-39). Now obviously if Jesus is going to be damned in their place by taking on the Father's undiluted full fury merited by the sins of James and John and all believers, then it's astonishing that Jesus would say they too will drink from the cup and be baptized with the baptism Jesus will undergo. So Lee's "solution" is that Jesus drank so we wouldn't have to, and that in fact Jesus turned the cup they will drink from wrath into something sweet and refreshing. This is quite ridiculous and is clearly a desperate attempt to get around the text. Jesus is clearly issuing a challenge here, not an invitation to have a relaxing drink.
The only way you can read the text at face value is if you abandon the God's Wrath interpretation and abandon Penal Substitution. The text is simply saying this 'cup' and 'baptism' Jesus will undergo are figurative descriptions for persecutions at the hands of the Jews and Romans for the sake of the Gospel, as the Gospel accounts plainly teach. And Jesus is saying James and John will drink and be baptized both as a prophecy and as a warning that they too will undergo persecutions for the sake of the Gospel (as they surely did!). So there's no difficulty here at all if you're not following traditions of men on this point.
It's sad to see the way the typical Protestant reading of such texts nullify the teachings of Our Lord and make nonsense of them. It's a wonder that Protestants can really explain Christ's teaching when He said other challenging things such as:
If anyone would come after me, let him deny himself and take up his cross daily and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake will save it. (Luke 9:23-24)
Now if the Cross is about Jesus enduring the Father's undiluted full wrath upon Himself so that we wouldn't have to, why in the world is Jesus demanding that anyone who wants to be a Christian must "take up their cross"? I feel that such passages cannot be explained by the Protestant (Calvinist) paradigm, which would also explain why Protestants typically ignore such texts all together. But such texts are quite beautiful if one would simply follow Scripture instead of traditions of men by dropping the Penal Substitution motif all together. As with the Cup/Baptism account, the Cross is that of suffering persecutions and life's hardships out of love for God. And with this, it makes perfect sense for Jesus to make it a requirement for each of us to carry our cross daily.
 Even if it were granted that the 'cup' Jesus spoke of in the Gospels was in some way linked to the "cup of God's wrath" referenced in Jeremiah 25:15 and Isaiah 51:17, this wouldn't support the Protestant reading anyway. This is because the "wrath" referenced in those Old Testament texts is not that of damnation to hellfire, but rather temporal physical persecutions which God sent upon Israel (Jeremiah 25:28-29). This wrath was not just confined to those evil doers, but it was a blanket condemnation on the whole area, even the innocent (including OT prophets) had to endure the suffering hitting the whole region, e.g.: "If those who did not deserve to drink the cup must drink it, will you go unpunished?" (Jeremiah 49:12). Clearly such texts cannot mean God damned those "who did not deserve" it. So with this in mind, Jesus could drink the 'cup' of God's judgment upon all creation, namely living in this fallen world with all it's miseries, including the punishment effects of suffering and death which we are all subject to endure ourselves.