Parshas Va'eira - The Makos Are All Mida K'Neged Mida
Hashem
punishes Mida K'Neged Mida. In Mitzrayim Hashem punished the Mitzrim
with the 10 Makos. Each one was Mida K'Neged Mida for something that
the Mitzrim did to Bnei Yisroel. Nothing was random. There are many
Medrashim and Peirushim including the Kli Yakar and Abarbanel who
explain what each Maka was for. In the Hagadah Otzer HaMedrashim it
brings a number of explanations for each.