They shall wash their hands and their feet repeats the same words used in verse 20. Lest they die is identical with verse 20. This repetition is for emphasis, so Good News Translation has “They must wash their hands and feet….”

It shall be a statute for ever to them is literally “and it shall be for them an obligation of long time.” The word for statute, choq, is discussed in the introduction to 20.22-26. Them, of course, refers to Aaron and his sons. Even to him, literally “to him” (even is added), refers to Aaron. And to his descendants, literally “and to his seed,” is the same word used in 28.43. Throughout their generations, literally “to their generations,” may be understood as “in every generation” (Revised English Bible), “throughout the ages” (New Jewish Publication Society’s Tanakh), or simply “forever” (Good News Translation).

An alternative translation model combining verses 17-21 is the following:

• The LORD said to Moses, “Have them make a large bronze bowl and a bronze stand for it. Then put the bowl between the sacred tent and the altar for sacrificing animals. Put water in the bowl so that the priests can wash their hands and feet before they enter the tent or sacrifice an animal on the altar. They and their descendants must always wash themselves in this way. Otherwise they will die [or, be killed].”

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 .