And the sons of Levi is better understood as “the Levites” (Good News Translation), or “The men of the Levi tribe” (Contemporary English Version). (See the comment at verse 26.) Did according to the word of Moses is literal, using the noun davar (“word”). But it may be more natural to say “did as Moses commanded” (New Revised Standard Version), or “followed his orders” (Contemporary English Version), or simply “the Levites obeyed” (Good News Translation).

And there fell of the people that day is literally “and he [or, it] fell from the people in that day.” The word is often used for falling in battle. This, of course, means that they were “killed” (Good News Translation). About three thousand men means approximately three thousand males. The word for men (ʾish) usually distinguishes them from the women, but this is not explicit here. Probably some women were among those killed, even though Moses commanded the sons of Levi to kill their brothers (verse 27). Some translations therefore translate “people” instead of men (New International Version, Revised English Bible, New Revised Standard Version, and others). In languages that do not use the passive voice, one may follow Good News Translation‘s model and say “The Levites obeyed, and killed about three thousand men that day.”

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 .