Luke 23:3

And Pilate asked him, saying, Art thou the King of the Jews? And he answered him and said, Thou sayest.

Luke's record, like all of the Gospels, omits some things found in the others and includes some things not found in the others, the only proper understanding of such records being found in the composite record of all four Gospels.

As Spence noted, the very first thing Pilate did was to attempt an avoidance of condemning Jesus, or even judging him at all.

"Take ye him, and judge him according to your law" (John 18:31); to which the Sanhedrinists replied that they were not allowed to put any man to death ... revealing their deadly purpose in the case of Jesus.[3]

Some have understood this verse as indicating Pilate's willingness to accept the third charge against Jesus (that he laid claim to being a secular king), that being the reason for the question here; but that simply cannot be true. As Ash observed: "Pilate knew the Jews would follow a king, not deliver him up."[4] Thus, the third charge was as clearly false in Pilate's understanding of it, as were the others. If Jesus had been what the Sanhedrin said he was, a claimant of secular kingship, they would have followed and supported him unto death. In fact, some of those very hypocrites had spent an entire day trying to get Jesus to be the quartermaster of a secular army against Rome (see in John 6). Thus Pilate's pinpointing the third charge had no reference to his being taken in by such a lie, but rather shows his astonishment at it.

Thou sayest ... This has been interpreted as noncommittal, a denial, and as an affirmation of Jesus' kingship, the latter being the true meaning. From John, it is learned that the Lord explained thoroughly to Pilate that his kingdom was not of this world. There is no evidence at all that Pilate ever doubted Jesus' word on this. See under Luke 23:38. This is proved by Pilate's immediate announcement of Jesus' innocence.

[3] H. D. M. Spence, The Pulpit Commentary (Grand Rapids, Michigan: Wm. B. Eerdmans Publishing Company, 1962), Vol. 16, Luke, p. 235.

[4] Anthony Lee Ash, The Gospel according to Luke (Austin, Texas: Sweet Publishing Company, 1972), p. 135.