John 13:18-19

Again Jesus limited what He had said to those disciples who truly believed on Him (John 13:10; cf. John 6:71; John 12:4; John 13:2). He made this statement so that when the disciples would later remember His words they would not think that He had been mistaken about Judas. Instead they would believe that Jesus was "I am," connoting deity (Exodus 3:14; Isaiah 41:4; Isaiah 43:10; cf. John 8:24; John 8:28; John 8:58). He wanted the disciples to believe His claims before His crucifixion apparently invalidated them and before His resurrection confirmed them.

Jesus chose Judas as one of the Twelve to fulfill Psalms 41:9. The Son of David experienced treason from a close friend as the original David had. Perhaps the betrayer of David in view was Ahithophel, who also committed suicide (2 Samuel 15:12; 2 Samuel 16:15-23; 2 Samuel 17:3-4; 2 Samuel 17:14; 2 Samuel 17:23). Betrayal by one who had received table hospitality was especially heinous in the ancient Near East. Lifting up the heel against someone was probably a way of saying that one had walked out on his friend. [Note: Bruce, pp. 287, 296, footnote 14.] Other possibilities are that the expression derived from the lifting up of a horse’s hoof preparatory to kicking, [Note: Tasker, p. 161.] or it alluded to shaking off the dust from the feet (cf. Luke 9:5; Luke 10:11). [Note: Morris, p. 553.]