And the one who burns it shall wash his clothes in water and bathe his flesh in water, and he shall be unclean until evening.
Torah Temimah: Sifrei — Why does it say “and the one who burns it”? The verse comes and teaches concerning all who deal with the para from beginning to end that they require washing of clothes, immersion of the body, and waiting until evening.
English: Why does it say “and the one who burns it”? The verse comes and teaches concerning all who deal with the para from beginning to end that they require washing of clothes, immersion of the body, and waiting until evening.
Expansion from the specific case of the burner to all handlers.
Everyone who participates in any stage of the para aduma process — from the beginning to the end — becomes impure and must wash clothes, immerse, and wait until evening.