This can be stated in active form. Alternate translation: "if the fire destroys anyone's work" or "if the fire ruins anyone's work" (See: [[rc://en/ta/man/jit/figs-activepassive]])
The abstract noun "loss" can be expressed with the verb "lose." Alternate translation: "he will lose his reward" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])