Then is the usual conjunction waw, but here as in verse 19 it clearly indicates the next event in sequence. Moses stretched out his hand uses the same verb as in 16. We may assume that his staff was in that hand. Over the sea is the same as verse 16. Moses’ action was only the signal for Yahweh to take over.

And the LORD drove the sea back is literally “and Yahweh caused the sea to go.” The idea of back is implied in the following verses. Revised English Bible has “drove the sea away,” and New American Bible has “swept the sea.” By a strong east wind means “with, or by means of, a strong wind blowing from the east.” (See 10.13.) All night means “throughout the night” (New American Bible). This refers only to the wind, not to Moses holding out his hand. In many languages translators will need to restructure the first part of this verse; for example, “The LORD caused a wind to blow strongly from the east. It blew all night.”

And made the sea dry land uses a word that means to put or place, or to make. New Revised Standard Version has “turned the sea into dry land,” but this is not the word used in 7.17 and 20 for turning the water into blood. It was not the water that was transformed, but rather the “seabed.” The water was blown away and Yahweh “turned the seabed into dry land” (Revised English Bible). Other ways to express this are “It blew the water back so that dry land appeared” or “that blew all night until there was dry land where the water had been” (Contemporary English Version). And the waters were divided uses the same word, “to split,” as in verse 16, but here the plural waters is used. This may be changed to the singular, as in Translator’s Old Testament, “The water was split apart.” Contemporary English Version has “the sea opened up.” Note that Translator’s Old Testament, Today’s English Version, Contemporary English Version, and others connect this clause with the following verse.

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 .