So Moses went down from the mountain to the people marks the third descent of Moses from the mountain. (See the comment on verses 9b-10.) Since went down suggests that the narrator is located on top of the mountain, it is better to locate the narrator at the bottom and say, as Good News Translation translates, “Moses came down the mountain….” And consecrated the people uses the same words as verse 10. And they washed their garments is also the same as in verse 10. (See the comment there.)

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 .