John 13:27

And after the sop, then entered Satan into him. Jesus therefore saith unto him, What thou doest, do quickly.

The entering of Satan into Judas at this time indicates an unusually malevolent entry; because Satan had been in Judas before, as for example, when he bargained for the thirty pieces of silver. Therefore, this indicates that Satan took possession of Judas permanently, in consequence of his judicial hardening, a fact suggested, and even demanded, by the fact of Jesus' command for Judas to act quickly. Until this point, there had been hope for Judas; but, after Satan took him over, his descent into wretchedness and death was swift, dramatic, and irrevocable. The example of what happened to Judas here should give every person pause in the contemplation of evil. Once the die is finally cast and Satan claims possession of the soul, swift and inevitable destruction always ensues. Another example of this same ruthless destruction on the part of Satan is seen in the case of the demons being permitted to enter the swine (Matthew 8:32).

What thou doest, do quickly ... God will not always oppose the will of evil men. There comes the day when Balaam is commanded to "Go with the men" (Numbers 22:22), and Judas is ordered to get on with the betrayal.

The sop ... is repeatedly mentioned here and cannot fail to emphasize the triviality of Judas' reward. It was a mere trifle, a financial sop, a mere handful of change that he received for betraying the Saviour.