The abstract noun "atonement" can be stated as a verb. Alternate translation: "The priest will atone for him" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])
This means Yahweh will forgive the person, not the priest. This can be translated in active form. Alternate translation: "God will forgive him" (See: [[rc://en/ta/man/jit/figs-activepassive]])