משך חכמה — בעבור זה עשה ה' לי בצאתי ממצרים

Q — What does the demonstrative "זה" refer to — "in order for WHAT did Hashem take me out of Egypt"?

A — A father investing in his daughter's match cannot tell whether his investment was worthwhile until the husband himself toils in sweat to provide for her; so too Hashem's question of whether the Exodus was "worth it" is answered only when Israel keep mitzvot under the strain of working the land — and even more profoundly in galut, when they keep all the laws of the chag with only matzah and maror before them and no Pesach.