John 13: 18-30, Night

Jesus has entered the upper room for the Passover Feast.  There he washes the disciples' feet and explains that one will betray him.

John 13:18-30, A traitor in our midst
“I am not referring to all of you; I know those I have chosen. But this is to fulfill this passage of Scripture: ‘He who shared my bread has turned against me.’

19 “I am telling you now before it happens, so that when it does happen you will believe that I am who I am. 
20 Very truly I tell you, whoever accepts anyone I send accepts me; and whoever accepts me accepts the one who sent me.”

From the NIV footnotes: the phase translated "turned against me" is literally "lifted up his heel."  This is a quotation from the Old Testament, from Psalm 41:9. One more indicator that Jesus is the Messiah (so he says) is that he has planned the upcoming events. He knows that he will be betrayed and knows that he will die.

John 13:21-30, A traitor in our midst
After he had said this, Jesus was troubled in spirit and testified, “Very truly I tell you, one of you is going to betray me.”

22 His disciples stared at one another, at a loss to know which of them he meant. 
23 One of them, the disciple whom Jesus loved, was reclining next to him. 
24 Simon Peter motioned to this disciple and said, “Ask him which one he means.”

25 Leaning back against Jesus, he asked him, “Lord, who is it?”

26 Jesus answered, “It is the one to whom I will give this piece of bread when I have dipped it in the dish.” Then, dipping the piece of bread, he gave it to Judas, the son of Simon Iscariot. 
27 As soon as Judas took the bread, Satan entered into him.

So Jesus told him, “What you are about to do, do quickly.” 
28 But no one at the meal understood why Jesus said this to him. 
29 Since Judas had charge of the money, some thought Jesus was telling him to buy what was needed for the festival, or to give something to the poor. 

Although Jesus knows the night's events, he is distressed. The disciple "whom Jesus loved" is presumably John, the author of this gospel. Peter presses John to pass on a question; John does and Jesus responds by dipping bread in a dish and giving it to Judas.  Then Jesus has quiet instructions to Judas, misunderstood by the few who hear it.

John 13: 30, Judas leaves, into darkness
As soon as Judas had taken the bread, he went out. And it was night.

There is poetry in John's writings.  As soon as Judas leaves, there is darkness.  We are approaching the darkest day, now called "Good Friday".