ולא יזח החשן מעל לאפד…(תצוה כח:כח)

The Choshen corresponds to the heart, as the passuk says, “והיו על לב אהרן” — that it rested upon Aharon’s heart. Additionally, the gematria of the word “אפוד” equals that of “פה” (mouth), hinting that the mouth must remain connected to the heart. When a Yid seeks to serve Hashem, there must be harmony between heart and mouth. A person’s words should faithfully express what he truly feels and believes within his heart.