en_tn/jhn/13/18.md

this is so that the scripture will be fulfilled

With this sentence, Jesus introduces something he will tell them in verse 21 that fulfills what the scripture says. You can translate this in an active form. Alternate translation: "this is in order to fulfill the scripture" (See: rc://en/ta/man/jit/figs-activepassive)

the scripture

"this scripture"

He who eats my bread lifted up his heel against me

Jesus quoted the scripture that will be fulfilled. Here the phrase "eats my bread" is an idiom for someone who pretends to be a friend. The phrase "lifted up his heel" is also an idiom, which means someone who has become an enemy. If you have idioms in your language that have these meanings, you can use them here. Alternate translation: "The one who has pretended to be my friend has turned out to be an enemy" (See: rc://en/ta/man/jit/figs-idiom)