Explanation and summary
The seventh plague of the 10 plagues that the God of the Israelites sent as judgment upon Egypt, through Moses, was a hailstorm, as recorded in the book of Exodus. In this plague, hailstorms kill all slaves and animals not brought under cover in response to the warning that this calamity was coming. These storms also destroyed vegetation. The Egyptian gods insulted by this plague include Seth (an earth god), Nut (the sky goddess), Serapis (the god of fire and water), and perhaps others as well.
Hail is rare in Egypt, but is not unknown. The writer has himself seen a very little, and has known of one instance when a considerable quantity of hail as large as small marbles fell. Lightning, also, is not as frequent in Egypt as in many semi-tropical countries, yet great electric storms sometimes occur. This plague is quite accurately dated in the seasons of the year (Exodus 9:31, Exodus 9:32). As the first plague was just before the rising of the Nile, so this one is evidently about 9 months later, when the new crops after the inundation were beginning to mature, January-February.
This plague also marks another great step forward in the revelation of Yahweh to Israel and to the Egyptians. First only His power was shown, then His wisdom in the timing of the plagues, and now His mercy appears in the warning to all godly-disposed Egyptians to save themselves, their herds and their servants by keeping all indoors (Exodus 9:19-21 ). Pharaoh also now distinctly acknowledged Yahweh (Exodus 9:27 ).
Biblical Text (KJV)
13 And the Lord said unto Moses, Rise up early in the morning, and stand before Pharaoh, and say unto him, Thus saith the Lord God of the Hebrews, Let my people go, that they may serve me.
14 For I will at this time send all my plagues upon thine heart, and upon thy servants, and upon thy people; that thou mayest know that there is none like me in all the earth.
15 For now I will stretch out my hand, that I may smite thee and thy people with pestilence; and thou shalt be cut off from the earth.
16 And in very deed for this cause have I raised thee up, for to shew in thee my power; and that my name may be declared throughout all the earth.
17 As yet exaltest thou thyself against my people, that thou wilt not let them go?
18 Behold, to morrow about this time I will cause it to rain a very grievous hail, such as hath not been in Egypt since the foundation thereof even until now.
19 Send therefore now, and gather thy cattle, and all that thou hast in the field; for upon every man and beast which shall be found in the field, and shall not be brought home, the hail shall come down upon them, and they shall die.
20 He that feared the word of the Lord among the servants of Pharaoh made his servants and his cattle flee into the houses:
21 And he that regarded not the word of the Lord left his servants and his cattle in the field.
22 And the Lord said unto Moses, Stretch forth thine hand toward heaven, that there may be hail in all the land of Egypt, upon man, and upon beast, and upon every herb of the field, throughout the land of Egypt.
23 And Moses stretched forth his rod toward heaven: and the Lord sent thunder and hail, and the fire ran along upon the ground; and the Lord rained hail upon the land of Egypt.
24 So there was hail, and fire mingled with the hail, very grievous, such as there was none like it in all the land of Egypt since it became a nation.
25 And the hail smote throughout all the land of Egypt all that was in the field, both man and beast; and the hail smote every herb of the field, and brake every tree of the field.
26 Only in the land of Goshen, where the children of Israel were, was there no hail.
27 And Pharaoh sent, and called for Moses and Aaron, and said unto them, I have sinned this time: the Lord is righteous, and I and my people are wicked.
28 Intreat the Lord (for it is enough) that there be no more mighty thunderings and hail; and I will let you go, and ye shall stay no longer.
29 And Moses said unto him, As soon as I am gone out of the city, I will spread abroad my hands unto the Lord; and the thunder shall cease, neither shall there be any more hail; that thou mayest know how that the earth is the Lord's.
30 But as for thee and thy servants, I know that ye will not yet fear the Lord God.
31 And the flax and the barley was smitten: for the barley was in the ear, and the flax was bolled.
32 But the wheat and the rie were not smitten: for they were not grown up.
33 And Moses went out of the city from Pharaoh, and spread abroad his hands unto the Lord: and the thunders and hail ceased, and the rain was not poured upon the earth.
34 And when Pharaoh saw that the rain and the hail and the thunders were ceased, he sinned yet more, and hardened his heart, he and his servants.
35 And the heart of Pharaoh was hardened, neither would he let the children of Israel go; as the Lordhad spoken by Moses.
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).