Albert Barnes Commentary John 18:28

"They lead Jesus therefore from Caiaphas into the Praetorium: and it was early; and they themselves entered not into the Praetorium, that they might not be defiled, but might eat the passover." — John 18:28 (ASV)

See Matthew 27:1-2.

Hall of judgment. The praetorium—the same word that in Matthew 27:27 is translated common hall.

It was the place where the Roman praetor, or governor, heard and decided cases brought before him. Jesus had been condemned by the Sanhedrin and pronounced guilty of death (Matthew 26:66); but they had no power to carry their sentence into execution (John 18:31), and they therefore sought that he might be condemned and executed by Pilate.

Lest they should be defiled. They considered the touch of a Gentile to be a defilement, and on this occasion, at least, seemed to regard it as a pollution to enter the house of a Gentile. They took care, therefore, to guard themselves against what they considered ceremonial pollution, while they were wholly unconcerned at the enormous crime of putting the innocent Saviour to death and imbuing their hands in their Messiah's blood.

Probably there is not anywhere to be found among humankind another such instance of petty regard for the mere ceremonies of the law, and attempting to keep from pollution, at the same time that their hearts were filled with malice, and they were meditating the most enormous of all crimes.

But it shows us how much more concerned people will be about the violation of the mere forms and ceremonies of religion than about real crime, and how they endeavor to keep their consciences at ease amid their deeds of wickedness by the observance of some of the outward ceremonies of religion—by mere sanctimoniousness.

That they might eat the passover (Matthew 26:17).

This defilement, produced by contact with a Gentile, they considered as equivalent to that of the contact of a dead body (Leviticus 22:4–6; Numbers 5:2), and as disqualifying them from partaking of the Passover in a proper manner. The word translated passover properly means the paschal lamb which was slain and eaten on the observance of this feast.

This rite Jesus had observed with his disciples the day before this. It has been supposed by many that he anticipated the usual time of observing it by one day, and was crucified on the day on which the Jews observed it; but this opinion is improbable. The very day of keeping the ordinance was specified in the law of Moses, and it is not probable that the Saviour departed from the commandment.

All the circumstances also lead us to suppose that he observed it at the usual time and manner (Matthew 26:17, 19). The only passage which has led to a contrary opinion is this in John; but here the word passover does not, of necessity, mean the paschal lamb. It probably refers to the feast which followed the sacrifice of the lamb, and which continued for seven days. Compare Numbers 28:16-17. The whole feast was called the Passover, and they were unwilling to defile themselves, even though the paschal lamb had been killed, because it would disqualify them from participating in the remainder of the ceremonies (Lightfoot).

The hall of judgment may also be referred to as "Pilate's house." For lest they should be defiled, compare Acts 10:28.