exodus 10:2 And that thou mayest tell in the ears of thy son, and of thy son's son, what things I have wrought in Egypt, and my signs which I have done among them; that ye may know how that I am the LORD. - Free Bible Online

      2. And that thou mayest tell . . . of thy son, and of thy son's son, &c.--There was a further and higher reason for the infliction of those awful judgments, namely, that the knowledge of them there, and the permanent record of them still, might furnish a salutary and impressive lesson to the Church down to the latest ages. Worldly historians might have described them as extraordinary occurrences that marked this era of Moses in ancient Egypt. But we are taught to trace them to their cause: the judgments of divine wrath on a grossly idolatrous king and nation.

JFB.