Psalm 41 (Douay-Rheims Psalm 40) grieves a treachery sharpened by intimacy: 'For even the MAN OF MY PEACE, in whom I trusted, WHO ATE MY BREAD, hath greatly supplanted me [lifted up his heel against me]' (41:9). David knew the wound personally — his counselor Ahithophel, who went over to Absalom and then hanged himself (2 Samuel 15–17), is the psalm's traditional backdrop and an eerie shadow of Judas down to the manner of death.
At the Last Supper, Christ cited the verse before the act: 'I speak not of you all: I know whom I have chosen. But that the scripture may be fulfilled: HE THAT EATETH BREAD WITH ME, shall lift up his heel against me. At present I tell you, before it come to pass: that when it shall come to pass, you may believe that I am he' (John 13:18–19). Then He dipped the morsel and gave it to Judas.
The detail the prophecy insists on is the shared bread — betrayal from inside the covenant meal. The Church has never forgotten where the verse was fulfilled: at the first Eucharist, with the betrayer's hand on the table (Luke 22:21).