English: “The sons of Aharon the kohen” — the kohen in his [proper] kehunah: this teaches that a Kohen Gadol who served in the garments of an ordinary kohen — his service is invalid.
In the sugya: “The kohen” after “sons of Aharon” points to rank-correct service. A Kohen Gadol in ordinary-kohen garments is not “the kohen” in his kehunah; the avodah fails.
Type of Learning
Diyuk from the extra word “the kohen” — garments must match rank.
What Is Learned
Avodah is valid only when the kohen wears the garments prescribed for his rank. A Kohen Gadol who serves in the garments of an ordinary kohen has invalid service. “The kohen” means the kohen in his proper kehunah.