And said to Moses continues the sentence from verse 18, so it is the people who are going to speak. You speak to us uses an emphatic You (singular), so New Jerusalem Bible has “Speak to us yourself” (also Revised English Bible, New International Version, Translator’s Old Testament). But it is also possible to have a conditional construction as in Good News Translation and Contemporary English Version, “If you speak to us….” And we will hear may be understood as “we will listen,” but the word also implies “we will obey” (New Jewish Publication Society’s Tanakh, New Jerusalem Bible). However, in some languages it will be necessary to state whom the people will obey or listen to. In this case it is probably Moses. So one may translate “If you speak to us, we will obey what you tell us to do.”

But let not God speak to us is literally “and God will not speak to us,” but it uses the negative marker for a command or a request. Therefore the people are requesting Moses to do something that will discourage God from speaking to them directly. It does not suggest that Moses had the power to prevent God from speaking to them. Contemporary English Version has “But don’t let God speak to us.” Lest we die expresses what the people fear will happen if God does continue speaking to them. As mere humans they will not be able to survive such an overwhelming experience of having a deity speak to them. The entire statement may be understood as in Good News Translation, “If God speaks to us, we will die,” or as Contemporary English Version says, “But don’t let God speak to us, or we will die!”

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 .