He that feared the word of the LORD among the servants of Pharaoh made his servants and his cattle flee into the houses:

Jamieson-Fausset-Brown Bible Commentary

20, 21. He that feared the word of the Lord . regarded not, &c.-Due premonition, it appears, had been publicly given of the impending tempest-the cattle seem to have been sent out to graze, which is from January to April, when alone pasturage can be obtained, and accordingly the cattle were in the fields. This storm occurring at that season, not only struck universal terror into the minds of the people, but occasioned the destruction of all-people and cattle-which, in neglect of the warning, had been left in the fields, as well as of all vegetation [Ex 9:25]. It was the more appalling because hailstones in Egypt are small and of little force; lightning also is scarcely ever known to produce fatal effects; and to enhance the wonder, not a trace of any storm was found in Goshen [Ex 9:26].

Matthew Henry's Concise Commentary

9:13-21 Moses is here ordered to deliver a dreadful message to Pharaoh. Providence ordered it, that Moses should have a man of such a fierce and stubborn spirit as this Pharaoh to deal with; and every thing made it a most signal instance of the power of God has to humble and bring down the proudest of his enemies. When God's justice threatens ruin, his mercy at the same time shows a way of escape from it. God not only distinguished between Egyptians and Israelites, but between some Egyptians and others. If Pharaoh will not yield, and so prevent the judgment itself, yet those that will take warning, may take shelter. Some believed the things which were spoken, and they feared, and housed their servants and cattle, and it was their wisdom. Even among the servants of Pharaoh, some trembled at God's word; and shall not the sons of Israel dread it? But others believed not, and left their cattle in the field. Obstinate unbelief is deaf to the fairest warnings, and the wisest counsels, which leaves the blood of those that perish upon their own heads.