פּירוש אויף שמות 28:35

ולא ימות THAT HE DIE NOT — From what is included in this negative statement you may infer the positive: if he has these garments on him he will not incur death; consequently if he enters the Sanctuary lacking one of these garments he incurs death at the hands of God (cf. Sanhedrin 83).

So that the sound of it is heard: So that he should not come before Me like a thief tunneling in. And we learn proper conduct from this, that a person should not enter his fellow's house suddenly, lest he is doing or saying something private. But if he hears him coming, he will [be able to] hide from him.

ונשמע קולו, “its sound would be audible;” [the High Priest did not wear these garments inside the Tabernacle on the Day of Atonement. Ed.] The sound was meant to alert the people that the time for him to perform the service in the Tabernacle had arrived. According to another interpretation, the sound was necessary to warn the other priests not to enter the Holy of Holies. On the Day of Atonement there was no need for it, seeing that only the High Priest performed sacrificial service on that day.