What does Exodus 9:31 mean?

These verses (Exodus 9:32) are often set in parentheses because they are side notes to the main story. The massive hailstorm (Exodus 9:24–25) has pulverized everything caught in the open. Only those people and animals who came indoors survived exposure to the disaster (Exodus 9:18–21). These notes explain that some Egyptian crops had been planted but hadn't sprouted. Or they were young enough that they could quickly regrow. Others were nearing the harvest and were wiped out. Here, flax and barley are in that mature state, so the hailstorm shreds them beyond saving.

Flax is used to make linen, necessary for clothing, especially for Egyptian priests. Linen bandages were often used for mummies, as part of sending the dead into the afterlife. Because linen had religious connections, some interpret this as part of God's judgment on the polytheism of Egypt.

Barley served as a major Egyptian crop, used for baking diverse types of foods. Barley could also be used to make alcoholic drinks, as well as food for horses.

Some commentators observe that harvest of these crops typically take place in January or February. This helps indicate the approximate date of this plague. Since the first Passover took place around early April, this was two or three months prior to the tenth plague (Exodus 12:2–14). The plagues of locusts and darkness (Exodus 10) also took place between these two events. If the first plague occurred in the fall of the previous year, the full cycle (Exodus 3:20) took place over several months. This would have been from around September to the following April. Despite this extended time of judgment, Pharaoh and his people continued to remain opposed to the freedom of Israel.