JOHN 13.21: After saying these things, Jesus was troubled in his spirit, and testified, “Truly, truly, I say to you, one of you will betray me.” …..(26) And Jesus answered, “It is he to whom I will give this morsel of bread when I have dipped it.” So when he dipped the morsel, he gave it to Judas, the son of Simon Iscariot. (27) Then after he had taken the morsel, Satan entered into him. Jesus said to him, “What you are going to do, do quickly.” …..(30) So, after receiving the morsel of bread, he immediately went out. And it was night.” (ESV)
The expression, “You Judas” is recognized as a statement that someone is deceitful and given to betrayal in any number of contexts. And such was the character of the original Judas for whom this expression came into recognition.
Comparing the above verses to the Gospel of Mark’s account, we can see that Judas had already agreed with the chief priests to betray Jesus over to them. During this time in the upper room Judas was just waiting for his opportune time to actually betray Jesus to the people who hated Him. And it also looks like Judas joined in with all the other disciples claiming that he would not be the one who will betray Jesus.
Previously in John 12.6, John states that Judas was a thief, because he would steal money from the moneybag that Jesus and His disciples had. Judas was a lover of money, and in his transaction with the chief priests he was to be paid the infamous 30 pieces of silver. And this compensation, which was offered by the chief priests at their initiative, was the fulfillment of the prophecy set forth in Zechariah 11.12.
And so with the agreement made by Judas with the chief priests, and after having been exposed by Jesus that he was the betrayer, Judas was an open vessel for Satan to enter and occupy. A terrible condition, but one brought about by his own choosing, greed, and actions.
When John says in verse 30, “and it was night”, it looks like the word “night” is being used to express the darkness in which Satan is at work at that moment, bringing to pass his works of evil against Jesus and His disciples. When Jesus was betrayed by Judas and arrested by the chief priests and their mob, He said to them in Luke 22.53: “But this is your hour, and the power of darkness.” (ESV)