On the way out of Mitzrayim, Moshe informs the people Jewish about many commandments surrounding their departure. He commands them to take matzah and sacrifice the korban Pesach, among others. He also commands them with the famous phrase, "v'higadita li'vincha," tell your children, the two words which serve as the basis for our annual Seder night.
The words which follow the commandment of "v'higadita li'vincha," the content of what to tell the children is a little less clear. "Ba'avur zeh asah Hashem li b'tzeisi mi'Mitzrayim," because of this G-d has acted on my behalf when I left Egypt (Artscroll). Rashi says that "zeh/this" refers to the mitzvos of korban Pesach and matzah. Seemingly, then, the pasuk is out of order; G-d has acted on my behalf, therefore I am performing these mitzvos.