Adam Clarke on Exodus 12:30

There was a great cry - No people in the universe were more remarkable for their mournings than the Egyptians, especially in matters of religion; they whipped, beat, tore themselves, and howled in all the excess of grief. When a relative died, the people left the house, ran into the streets, and howled in the most lamentable and frantic manner. See Diod. Sicul., lib. i., and Herod., lib. ii., c. 85, 86. And this latter author happening to be in Egypt on one of their solemnities, saw myriads of people whipping and beating themselves in this manner, lib. ii., c. 60; and see Mr. Bryant on the Plagues of Egypt, where many examples are given, p. 162, etc. How dreadful then must the scene of horror and distress appear when there was not one house or family in Egypt where there was not one dead; and according to their custom, all the family running out into the streets bewailing this calamity!