What does Exodus 7:17 mean?

The Lord provided Egypt's ruler, the pharaoh, with a command to release Israel (Exodus 5:1–3) and evidence to show that the command had divine authority (Exodus 7:8–10). Pharaoh refused (Exodus 5:4), and even rejected the evidence of the miracle (Exodus 7:11–13). Now Moses is being told to appear by the Nile, in the morning, to confront Pharaoh again (Exodus 7:14–16). He will explain that Pharaoh's stubbornness will result in a terrible disaster: ruining the water in Egypt by turning it into blood.

This verse emphasizes the purpose of the upcoming plague. God is not inflicting pain simply as revenge. The miraculous sign, though terrible and terrifying, is meant to demonstrate the Lord's power and convince Pharaoh to obey. Among the Egyptian deities were Hapi and Khnum, associated with the Nile. God's work here proves that He, not Khnum or Hapi, has power over the river.

Both the plague and the effects it brings are being predicted here, to drive home the point. The same staff used to perform the earlier miracle (Exodus 4:2–4; 7:10) will be used to trigger this new sign. Moses and Aaron will follow through on these commands (Exodus 7:20).

Egypt will suffer greatly for Pharaoh's obstinate heart (Expodus 7:21–25). The book of Exodus gives few details about the timing of these plagues. Some are stopped when Pharaoh pleads with Moses, but Pharaoh shows no concern about this first occurrence. It's possible that some of the next plagues—such as frogs and gnats—happen while the Nile is still ruined, and perhaps that God uses the corruption of the water to cause those later problems.