What does Exodus 7:25 mean?

Of the ten plagues (Exodus 3:19–20), only three are described with an explicit length of time. Water into blood lasts for a week; the number seven is associated with completeness and also with God. Darkness will last for three days (Exodus 10:21–22), and the death of the firstborn will happen in a single night (Exodus 11:4–5). Tradition typically assumes that the various disasters happened in a one-at-a-time sequence. However, Scripture does not say if, or how much, any of these catastrophes overlapped. It's possible that the corruption of the Nile drove frogs (Exodus 8:2–3) and small insects (Exodus 8:16) ashore, and that flies (Exodus 8:21), dead livestock (Exodus 9:3), and skin disease (Exodus 9:8–9) ran rampant as all these elements rotted.

Regardless of other problems, surface waters in Egypt will be unusable for drinking, bathing, or watering crops for a week. The Egyptians will be forced to scavenge for clean water so they don't die of thirst. Soon, they will face new challenges as their king remains obstinate (Exodus 8:15, 19, 32; 9:7) and uncaring (Exodus 7:23).

The Israelites lived in Goshen (Genesis 45:10; Exodus 8:22; 9:26), so likely did not suffer the effects of this plague. What effect this had on their slave work of brickmaking (Exodus 1:11–14) is not stated.