Then is the conjunction waw, which should be understood as placing the time of this verse during the worst part of the plague, not after the plague was over. Verse 29 indicates that the flies continued for another day. Pharaoh called Moses and Aaron is literally “he called to,” but it means “the king called for Moses and Aaron” (Good News Translation). One may say “he caused to be brought,” or “he caused his servants [or, them] to bring Moses and Aaron.” And said may need to be expanded to “and said to them” (New English Bible, New American Bible, Translator’s Old Testament), for this introduces what the Pharaoh said to Moses and Aaron.

Go and sacrifice are in the second person plural. Sacrifice to your God may mean either “offer a sacrifice” (singular) or “offer sacrifices to your God” (Good News Translation). This word is often used to describe the act of worship without indicating what kind of animal is killed. If necessary one may say “sacrifice an animal to your God.” (See 3.18b and comments.) Within the land means “here in Egypt” (Translator’s Old Testament), or “here in this country” (Good News Translation). The king, of course, was anxious to prevent the Israelites from leaving Egypt. Contemporary English Version‘s rendering clearly brings out this reluctance: “Go sacrifice to your God, but stay here in 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 .