He was referring to Judas, Simon Iscariot’s son, one of the Twelve, because he was going to betray Him.

Then one of His disciples, Judas Iscariot (who was about to betray Him), said,

Now by the time of supper, the Devil had already put it into the heart of Judas, Simon Iscariot’s son, to betray Him.

Jesus replied, “He’s the one I give the piece of bread to after I have dipped it.” When He had dipped the bread, He gave it to Judas, Simon Iscariot’s son.

Judas (not Iscariot) said to Him, “Lord, how is it You’re going to reveal Yourself to us and not to the world?”