What does John 13:27 mean?

This verse, understood in full context, is both tragic and terrifying. Judas has already made plans to turn Jesus over to His enemies (Matthew 26:14–16). All the same, Jesus has shown Judas friendship—even washing his feet (John 13:2–5) and sharing food (John 13:26). Given all Judas has seen and learned, it's heartbreaking to think he'd even consider something so vile.

That, in turn, adds to the terror of this moment. Like anyone else, Judas has lived with the options provided by a free will. But he's either ignored or resisted the truth for the entire time he's followed Jesus. He's opened himself to Satanic temptation and influence (John 13:2). Ultimately—horrifyingly—Judas has put himself in a position to be controlled by Satan entirely (Luke 22:3). Scripture indicates that those who resist God can expect sudden and irrevocable destruction (Proverbs 29:1). In this moment, Judas loses control of what he says and does—but he does so explicitly because of the sins and decisions he's already made.

Jesus became emotional when referring to this betrayal (John 13:21). He knows that in this moment Judas has, by his own choice, unquestionably crossed the point of no return (Mark 14:18–21).

The Greek phrasing Jesus uses in His statement to Judas / Satan is similar to the English phrase "hurry up." That might be another allusion to Jesus operating according to God's divine timetable (John 2:4; 7:30; 8:20; 12:23). Or, it might be Jesus implying something to the effect of "let's get this over with" (Luke 12:50; Matthew 26:36–39).