John 13:18

I speak not of you all.
] What he had before said on the one hand, "ye are not all clean", ( John 13:11 ) , for one of them was not; and on the other hand, when he put an "if" upon, or seemed to doubt of their knowing and doing these things, ( John 13:17 ) ; or what he was about to say concerning his being betrayed, this he did not speak of them all:

I know whom I have chosen;
not to apostleship, for they were all chosen to that, Judas as well as the rest, but to grace and glory, to everlasting salvation and happiness; of these he was well assured, that they were all clean, pure, and spotless, in the sight of God; were truly regenerated by the Spirit of God, and had an experimental and practical knowledge of the things he recommended by his example, and would be the happy persons he spake of;

but
he observes, so it is, and will come to pass, that there is one of you which will betray me:

that the Scripture may be fulfilled:
( Psalms 41:9 ) , as it literally ^F2 was in Judas's betraying Christ. The passage is by many interpreted either of Ahithophel, or of some other counsellor of Absalom's, or of Absalom himself; and is applied to their conduct, with respect to David, at the time of their rebellion against him; and which is thought to be typical of the treatment Christ met with from an apostle of his: but we do not find that, at the time of that rebellion, David was sick, or had any disease upon him, from whence they might hope for his death; it does not seem, as though it could be literally understood of David at all, and of the behaviour of any of his servants; but most properly of David's son, the Messiah, Jesus, with whom everything in the psalm agrees; and particularly this verse, which so plainly describes Judas, and expresses his base ingratitude, hypocrisy, and malice: the former part of the text is not cited, "yea, mine own familiar friend", or "the man of my peace, in whom I trusted"; though it fully agrees with him, he being admitted to great familiarity with Christ, and lived peaceably with him; and who was intrusted by him with the bag, into which the money was put, which was ministered, either for the sustenance of him and his apostles, or for the use of the poor: but our Lord thought fit to cite no more of it than what follows, that being sufficiently descriptive of him; and especially at this present time, when he was at table with his Lord.

He that eateth bread with me, hath lift up his heel against me;
he sat down with him at table frequently, and ate bread with him; and was doing so, when Satan put it into his heart to betray him; which is strongly expressed, by "lifting up" his "heel against him"; and sets forth the ingratitude, wickedness, and cruelty of him; who, like an unruly horse, that has thrown his rider, spurns at him, to destroy him; and also the insidious manner in which he did it; he supplanted, he tripped him, as wrestlers do, in order to cast him down to the ground, and then trample upon him, and triumph over him: he first (bram) , "laid snares for him", as Jarchi explains the phrase used in the "psalm", and then (lydgh) , "he magnified his heel", he behaved proudly and haughtily to him.