Commentators disagree on what actions will serve to prevent death from occurring. Vayikra Rabbah and Rashi view the final words of the verse ("וְלֹא יָמוּת") as related to the wearing of all of the priestly garments, the absence of any one of which would have fatal consequences. Rashbam, in contrast, understands the words to refer specifically to the ringing bells of the high priest's robe which would alert the ordinary priests to evacuate the Tabernacle while the purification rite was being performed. Finally, Ralbag also explains that the words relate to the bells, but he posits that the bells served to remind the high priest to mentally prepare for his year round service.
Wearing Full Attire
The high priest will not die if he wears all of the required vestments for serving in the Tabernacle, and the bells of the robe play no special role as far as this.
Context of "וְלֹא יָמוּת" – Rashi reads the words "וְלֹא יָמוּת" as referring to the high priest wearing all of the garments described in the entire chapter. He thus separates these words from the rest of the verse and their immediate context of the robe and the sounding of its bells.
Parallel verses – Vayikra Rabbah and Rashi view our verse as parallel to Shemot 28:43 which similarly describes a punishment of death for lack of proper attire.
Who might die? According to this interpretation, it is the high priest himself who might die if he is in violation of the priestly dress code.
Why is only the high priest commanded? According to Vayikra Rabbah and Rashi, the admonition against serving with improper attire applies equally to the high priest and to ordinary priests. Thus, there are two verses: 28:35 which refers specifically to the high priest as it comes in the context of the special vestments of the high priest, and 28:43 which relates to all priests as it follows the instructions regarding the basic priestly garments.
"הַקֹּדֶשׁ" – As this term appears in the first part of the verse speaking of the robe and its bells, it refers to the outer chamber in which the high priest would wear the golden garments. The prohibition of being dressed inappropriately, though, applies in all parts of the Tabernacle including the Holy of Holies, and even in the courtyard.
Function of the bells – Vayikra Rabbah views the ringing of the bells as part of appropriate manners to knock before entering the Tabernacle. The lack of such etiquette, though, might not warrant the death penalty. Rashi adds that when the high priest would enter the Holy of Holies and would not be wearing the robe with its bells, a special metallic attachment to the censer would instead serve to make the ringing entry sound.
Evacuation of the Sanctuary
The bells of the high priest's robe served as a warning call to all those present in the Sanctuary so that they knew to exit prior to the high priest's entry. This evacuation was either for the protection of other ordinary priests or for the high priest himself.
Rashbam asserts that the concern is lest an ordinary priest die due to his presence in the Sanctuary while the high priest is atoning for the nation.2
According to Ramban and R. Bachya, it is the high priest himself who is in mortal danger. The Tabernacle is normally filled with God's ministering angels who must evacuate before the high priest enters so that they do not harm him.
Parallel verses – According to this approach, the verse in Shemot is integrally related to the command of Vayikra 16:17, "וְכָל אָדָם לֹא יִהְיֶה בְּאֹהֶל מוֹעֵד בְּבֹאוֹ לְכַפֵּר בַּקֹּדֶשׁ". Rashbam assumes the verse refers to ordinary priests, while Ramban and R. Bachya understand the phrase "וְכָל אָדָם" to also include angels who are described in Yehezkel 1:10 as having "פְּנֵי אָדָם".
"הַקֹּדֶשׁ" – Rashbam maintains that "הַקֹּדֶשׁ" refers to the Holy of Holies, which the high priest entered on the Day of Atonement, whereas Ramban and R. Bachya, in contrast, assert that it refers just to the "Holy." They attempt to prove this from the fact that on the Day of Atonement the high priest did not enter the inner chamber with his robe and accompanying bells.
Entering the inner sanctum with robes? – Rashbam does not address the difficulty posed by the fact that on the Day of Atonement the high priest would not have been wearing his belled robe upon entering the Holy of Holies. One might suggest several solutions:
Ibn EzraVayikra 16:4About R. Avraham ibn Ezra on Vayikra 16:4 learns from our verse that on the Day of Atonement the priest did actually wear the garments mentioned here (the robe, tunic, and breastplate) into the inner chamber.3
Alternatively, one might suggest that there was a change in the law. Perhaps, initially the high priest was to be allowed into the Holy of Holies whenever he wanted, wearing his regular uniform. Only after the sin of Nadav and Avihu did Hashem limit entry to one day a year, and with specific garments.4
Why is only the high priest commanded?
According to Rashbam, it is only logical that the high priest alone wear the bells as he is the one who needs to warn the other priests.
According to Ramban and R. Bachya, one might have thought that any priest entering the "Holy" should similarly have to evacuate the ministering angels. Ramban suggests that the command is aimed just at the high priest due to his higher stature and greater service.
–
Proper Respect or Intentions
The ringing of the bells insured that the high priest approached his service in the Tabernacle with proper respect and purity of thought, and thus he would not perish.
Function of the bells – According to R. Chananel and R"Y Bekhor Shor, the bells were the high priest's way of knocking to request permission to enter. For Ralbag, in contrast, the bells were a reminder to the high priest to properly channel his thoughts to the worship of Hashem.
Who might die? According to these commentators, it is the high priest himself who was in danger.
Why is only the high priest commanded? These commentators do not address this issue. Ralbag could explain that the high priest was held to a higher standard due to the importance of his role.
"הַקֹּדֶשׁ" – R. Chananel interprets this to refer to only the outer part of the Sanctuary. He adds that on Yom HaKippurim, there was a special dispensation for the high priest to enter without "knocking", apparently because of the closer relationship to Hashem on this day.