During the meal Christians traditionally call the last supper, Jesus announces that one of the disciples will betray him. Many other things would have been said and done that evening, but Matthew is only interested in the prediction of betrayal and the bread and wine. Matthew has already told his readers Judas approached the chief priests to betray Jesus. Jesus’s response to his anointing at Bethany may have prompted Judas to make this offer, but it is not clear what motivated Judas’s betrayal of Jesus.
The ESV properly translates the verb ἀνάκειμαι, “recline.” They are not sitting on chairs at a table (like the DaVinci painting). But they would be sitting on the outside of a u-shaped set of low tables (so that part of the painting is not bad). This arrangement allows for conversation during the meal.
When Jesus announces one of the disciples will betray him, they are all upset, and they all wondered if they were the betrayer (Matthew 26:20-22). The disciples have been “sorrowful” before in Matthew. In Matthew 17:23, when Jesus predicted his crucifixion, the disciples were “very sorrowful.”
In fact, Jesus says “Woe to the betrayer!” (26:24). Woe introduces a bad situation for someone. Jesus pronounced “woe” in several condemnations of the Pharisees in Matthew 23:13-29. There are several examples of people who are “better to not be born.” Job, for example, cursed the day he was born (Job 3:3). In 1 Enoch 38:2, sinners are “better off never born” since they end up in a place of torment.
If the title Son of Man is based on Daniel 7:14, then it is remarkable that anyone would (or could) betray the Son of Man. No one in the first century would imagine the Danielic Son of Man failing at his mission to judge the nations because someone betrayed him.
Jesus gives a sign: the one who has dipped his hand in the dish with him will be the betrayer (26:23). Judas seems to confirm this sign (26:25). But they all were sharing food, so how is this sign helpful? It is not appropriate to use a modern Seder and try to find a particular moment when Jesus said this. John Nolland suggests this is the appetizer stage of the meal (Matthew, 1066). Was Jesus sharing a bowl of hummus with Judas? The verb ἐμβάπτω is an aorist participle, suggesting the dipping is over and now Jesus is pointing out that it was a sign to the betrayer. But later, he points out that prior to sharing the unleavened bread, the lettuce or green herbs were dipped into a sauce “with which the words about the betrayal are associated” (Matthew, 1074).
Judas directly asks Jesus if he is the betrayer, using the title “rabbi” for Jesus. When the other disciples asked, they said “Lord.” Is this an indication Judas does not acknowledge Jesus as Lord? When Judas approaches Jesus in the Gethsemane, he will also call him rabbi. The title is not necessarily cold, nor does it indicate a lack of faith in Jesus. But Matthew presents the other disciples as calling Jesus Lord, and they too will flee and deny Jesus.
Writing many years after the event, John says Jesus dips a morsel of bread and hands it to Judas. When Judas took the bread “Satan entered him” (John 13:26-30). Then Jesus tells him to do what he is about to do quickly, and he goes off into the darkness. John comments that the disciples do not know why Judas left, thinking Jesus tasked him with giving a gift to the poor since he was the “keeper of the moneybag.” John wrote as an eyewitness many years after Judas’s betrayal and explain why Judas betrayed Jesus: Jesus told him to!
Jesus’s response is “you have said so” seems ambiguous. Sometimes this is interpreted as the English phrase “you said it,” implying agreement. When the high priest asks him directly if he is the Messiah, Jesus will similarly respond “you have said so.” In that case the high priest understands the response as agreement, Jesus has blasphemed! So here, Jesus’s ambiguous response to Judas is an agreement that Judas is the betrayer.