And they shall be upon Aaron, and upon his sons simply means “Aaron and his sons shall wear them” (New American Bible). This refers primarily to the “breeches” mentioned in verse 42, but it may also refer to all the vestments mentioned. Translator’s Old Testament has “Aaron and his sons must wear these breeches,” and Good News Translation has “Aaron and his sons shall always wear them.”

When they go into the tent of meeting is literally “in their entering unto the ʾohel moʿed,” which in this context obviously refers to the tabernacle. (But see the comment at 27.21 and at the introduction to 33.7-11.) Or when they come near the altar is literally “or in their approaching the altar.” (Use the same term used for altar at 27.1.) To minister in the holy place uses the verb meaning to serve in a cultic way, as in verse 35.

Lest they bring guilt upon themselves and die is literally “and they will not carry guilt and die.” The word for “carry” is translated as “bear” in verses 12 and 29-30, and “take upon himself” in verse 38. Here Revised Standard Version adds the words upon themselves. The word for guilt is the same as in verse 38. And die means “and in consequence die” (Durham), for death will be the result of the guilt they would incur. That is, Yahweh will condemn them for not obeying these rules, and their punishment will be death. New International Version has “so that they will not incur guilt and die.” New Jewish Publication Society’s Tanakh has “so that they do not incur punishment and die.”

Good News Translation interprets this in a more specific way: “so that they will not be killed for exposing themselves.” This may be what is intended, but it limits the warning to wearing the “breeches” rather than all the vestments. The idea of death as punishment for exposing oneself to the ground was probably based on the mysterious holiness of the altar and the holy place. It was not a matter of modesty, for the normal dress at that time did not include a special covering for the genital area. (See the comment at 20.26.)

This shall be a perpetual statute is literally “an obligation of long time.” This shall be is added to make the sentence complete. Good News Translation calls it “a permanent rule,” and New Jewish Publication Society’s Tanakh has “a law for all time.” (See the comment on statute, choq, in the introduction to 20.22-26.) For him and for his descendants after him refers to Aaron and to all his descendants (literally “his seed”), who are to be the official priests of Israel. Contemporary English Version has “This same rule applies to any of their descendants who serve as priests.” (See descendants and the comment at 1.1.)

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .