So the latter leaned back upon the breast of Jesus and said to him: “Lord, who is it?” 26 Therefore Jesus answered: “It is that one to whom I shall give the morsel that I dip.” And so, having dipped the morsel, he took and gave it to Judas, the son of Simon Is·car´i·ot. 27 And after the morsel then Satan entered into the latter. Jesus, therefore, said to him: “What you are doing get done more quickly.” 28However, none of those reclining at the table knew for what purpose he said this to him.
I could never wrap my head around this. Jesus tells them how he's going to point out his betrayer - then he does it - then John says noone knows why he said what he just said.