Exodus 9:20-21

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

He that feared ... regarded not ... Due premonition, it appears, had been publicly given of the impending tempest-the cattle seem 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. It was the more appalling that 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. It appears from the statement made (Exodus 9:20) that the previous plagues had made a salutary impression in some quarters, if not upon the haughty despot, at least upon many of his respectable and opulent subjects, by undermining their faith in the national idolatry, and convincing them of the existence and mighty power of Yahweh.