The Legends of Jews, Vol. II, p. 367

by Louis Ginzberg

The very monuments and statues erected to the memory of the first-born dead were changed into dust, which was scattered and flew out of sight... [footnote states sources as Pesikta...M'yocheset l'Rav Kehana, Piska 7, folio 65b; Midrash Pesikta Rabbati, Pesikta 17, folio 88b; Midrash Shemot Rabbah, chapter 18, paragraph 10]

In dealing out punishment to these aliens in the land of Egypt, God showed that he was at once the Master of the land and the Lord over all the gods of the nations, for if the slaves and the captives of war had not been smitten, they would have said, "Mighty is our god, who helped us in this plague." [footnote states sources as Mekilta Bo 13, 13b]

For the same reason all the idols of the Egyptians were swept out of existence in that night [of the tenth plague]. The stone idols were ground into dust, the wooden idols rotted and those made of metal melted away [footnote states sources as Mekilta Bo 13, 13b; Mekilta d' Rabbi Shim'on ben Yochai, pp. 13-14; Tashar Bo, 144b; Targum Yerushalmi Exod 12. 12 and Num. 33.4; Midrash Tankhuma Hakedem v'Ha-Yeshan V, 32; Sukkah 29a. Comp. vol. II, pp. 250 and 348, as well as vol. III, p. 10.], and so the Egyptians were kept from ascribing their chastisement to the wrath of their own gods. Likewise the Lord God slew the first-born of the cattle, for the Egyptians paid worship to animals, and they would have attributed their misfortunes to them. In all these ways the Lord showed them that their gods were but vanity.