And Moses said presents a problem, for it does not easily relate to the preceding verses. (Good News Translation‘s “then” may be misleading.) Neither does it identify the addressee. Obviously he is not responding to Yahweh, for he is announcing what the LORD had told him to say. But what follows is quite different from what Moses was told to say to the Israelites in verse 2. On the basis of verse 8, therefore, it is best to assume that he is now speaking “to the king” (Good News Translation). (See the introductory remarks above.)

Thus says the LORD is the messenger formula discussed at 4.22. About midnight is literally “around the middle of the night,” that is, halfway between sunset and sunrise. I will go forth means that Yahweh will be the one going forth, since this is a quote within a quote. In the midst of Egypt means “throughout Egypt” (New International Version), or “among the Egyptians” (New Jewish Publication Society’s Tanakh). It is also possible to use indirect speech here and say, for example, “Yahweh says that about midnight he will go through the land of Egypt.”

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 .