Yitro listens to Moshe and hears him relate all the great wonders that Hashem did for the Bnei Israel in Egypt. He is awed by what he hears and praises Hashem and says: בָּרוּךְ יְקֹוָק. He does not stop at that but adds that Hashem is great: כִּי בַדָּבָר אֲשֶׁר זָדוּ עֲלֵיהֶם “…for in the very matter in which [the Egyptians] had conspired against them… .” (Ex. 18,11)
Rashi explains this passage, based on the explanation of Onkelos. The greatness displayed here was that Hashem punished the Egyptians by the very thing that Pharaoh wanted to destroy the Jews. He wanted to drown the Jewish children in the Nile and Hashem turned this intention around and brought it upon the Egyptians. It was Pharaoh’s army that drowned in the Red Sea. This is a principle that Chazal teach us Hashem uses in this world, namely, the principle of מדה כנגד מדה, measure for measure.
In our own conduct we must be ever mindful that often we fall prey to our own actions. We often do things that come back to haunt us. Before doing or saying something to spite someone, think twice. The action or the words can eventually turn around and do harm to our own selves.