A Yisroel needs to give kovod and honor a Kohen by according him service first, allowing the Kohen to go in front of a Yisroel and generally honoring the Kohen with kibudim before a Yisroel. The same principle applies regarding the Hamon Hoam honoring Talmidei Chachomim first and allowing him to go first; and the same applies regarding women honoring men and allowing him to go first.
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