John Calvin on Exodus 9:31-33

31. And the flax and the barley. He relates the calamity which the hail inflicted; and shows that a part of the fruits of the earth was destroyed, viz., that which had already grown into stalk; but that the seeds which grow more slowly were spared. For God desired to give a remnant of hope, which might invite the king and his people to repentance, if only their wickedness were curable.