This verse recalls and summarizes the story about Nadab and Abihu, which is narrated in Lev 10.1-7.

But Nadab and Abihu died before the LORD means they died in the Tent of Meeting, where the LORD manifested his presence in Israel, so Bible en français courant says “But Nadab and Abihu died before the sanctuary,” De Nieuwe Bijbelvertaling has “Nadab and Abihu had died near the sanctuary,” and New Jerusalem Bible translates “Nadab and Abihu died in Yahweh’s presence.” These versions give a better interpretation of the Hebrew here than New Jewish Publication Society’s Tanakh, which says “But Nadab and Abihu died by the will of the LORD.” The Hebrew conjunction rendered But is literally “And” (King James Version). Like Revised Standard Version, many translations use a contrastive connector here since the death of Nadab and Abihu comes as a contrast to verse 3, where their ordination is mentioned in the genealogy.

When they offered unholy fire before the LORD in the wilderness of Sinai: The Hebrew verb for offered is hiqrib, which is a technical term referring to the offering of a sacrifice. It is used here even though Nadab and Abihu’s offering was not authorized. More accurately, the Hebrew word translated unholy means “prohibited,” “alien,” or “strange” (King James Version). The fire was “unauthorized” (New International Version, New Jerusalem Bible), “unacceptable” (Contemporary English Version), because it had not been taken from the altar (compare Lev 16.12). Nadab and Abihu did not prepare the fire according to the ceremonial regulations of the Mosaic Law. For the wilderness of Sinai, see 1.1.

And they had no children: Not only did Nadab and Abihu die, but they died childless, so their lineage came to an end. They received a double punishment as it were, in contrast to Eleazar and Ithamar.

So Eleazar and Ithamar served as priests in the lifetime of Aaron their father: In the lifetime of Aaron their father (literally “on the face of Aaron their father”) may mean “while Aaron their father was still living” (compare Gen 11.28). However, the text does not seem to imply that Eleazar and Ithamar replaced Aaron as priests during his life. A number of translations interpret this phrase differently; for example, King James Version has “in the sight of Aaron,” NET Bible says “in the presence of Aaron their father,” and Contemporary English Version translates “with their father Aaron.” These renderings are more plausible here. Equally plausible are “under their father Aaron” (German common language version [Die Bibel im heutigen Deutsch], Luther) and “under the supervision of their father Aaron” (Zürcher Bibel, Willibrordvertaling).

Quoted with permission from de Regt, Lénart J. and Wendland, Ernst R. A Handbook on Numbers. (UBS Helps for Translators). Miami: UBS, 2016. For this and other handbooks for translators see here .