The ear signified that the kohen had to hear and heed the troubles of his community, the hand that he had to give them their needs, and the foot that he had to hasten to fulfil whatever his people required.
The kohen was not only an officiant who carried out the intricate ritual. He was also a spiritual leader who built up a rapport with his community. They listened to him because he listened to them. They supported him because he supported them. They hastened to help him because he hastened to help them.
The rabbi of later ages was not automatically a kohen. Learning and not lineage was the deciding factor in his appointment. But like the kohen, the rabbi had to understand his people as they had to try to understand him. People judged their rabbi more by his deeds than his words.