Exodus 9:18
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. 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.
The time is fixed to tomorrow about this time for a rain of very grievous hail, unlike any hail in Egypt since its foundation and establishment as a nation. The warning came through Moses early in the morning calling Pharaoh to let the Hebrews go to serve God, declaring plagues upon his heart and his servants and his people so he would know there is none like God in all the earth. Though God could have smitten Pharaoh and his people with pestilence and cut them off, He raised Pharaoh up to show His power and to declare His name throughout all the earth, while Pharaoh still exalted himself against Israel.
The plague was announced in advance so its coming could not be dismissed as chance. Joined to the announcement was a merciful command to gather into houses, barns, and sheltered places the cattle, servants, people, and everything in the field, because man and beast left in the field would die. The announcement divided those who feared and believed the word of the Lord and fled indoors from those who did not regard it and like Pharaoh left servants and cattle exposed. It tested exalted Egyptian pride and revealed whose hearts were affected by God's dealings, and this provided way of escape shows mercy in the midst of judgment.
The storm came as predicted with thunder and lightning and fire running along the ground mingled with very grievous hail. It smote throughout Egypt all man and beast in the field and every herb and broke and shattered every tree, bringing the first loss of Egyptian life with death and desolation following the destroying angel, while only in Goshen where Israel was there was no hail. The hail shows that the whole earth and the forces of nature are under the command of the God of the Hebrews and even the elements obey His voice. Afterward Pharaoh humbled himself and confessed sin and that the Lord is righteous and asked for entreaty and intercession that the thunder, hail, and lightning would cease, and Moses spread out his hands for the storm to stop so Pharaoh would know the earth is the Lord's. Moses knew beforehand that Pharaoh and his servants would not yet fear God, and after the plague was stayed Pharaoh refused to let Israel go because continual opposition had hardened his whole being in rebellion. The hail is an example of disaster falling on those who remain exposed rather than heed a warning, teaching that the only true safety of nations and individuals is obedience to the voice of God and standing on the side of truth and righteousness.