Exodus 13:8

And thou shalt instruct thy son on that day, saying, This precept is on account of what the Word of the Lord did for me in miracles and wonders, in bringing me forth from Mizraim.

Because of this Hashem did this for me. This should be understood: “For the sake of this service—i.e. the eating of the matzoh and the refraining from leaven bread, which were the first commandments that B’nei Yisrael received—Hashem performed for us miracles and took us out of Egypt.” In other words, Hashem only took B’nei Yisrael out of Egypt in order that they should serve Him, in keeping with the verse, “When you bring the people out of Egypt—you will serve Elohim on this mountain” (Shemos 3:12).

IT IS BECAUSE OF THAT THE ETERNAL DID FOR ME. This is equivalent to saying, “It is because of that which the Eternal did for me when I came forth out of Egypt.” A similar case is the verse: And thou shalt show them the way they are to go in, [which means “wherein they are to go”]. There are many such cases. The father is thus stating [to his son]: “It is because of that which G-d did for me when I came forth out of Egypt that I observe this service.” It is similar to that which is stated further on: Therefore I sacrifice to the Eternal all that openeth the womb.
The intent of the word zeh (that) [in the verse, It is because of ‘that’], is: “tell him ‘that’ which you yourself see, i.e., what G-d did for you when you came forth out of Egypt.” And our Rabbis have explained that the word zeh (that) alludes to the unleavened bread and bitter herbs that are laid before him.
It is possible that the purport of the verse, And thou shalt tell thy son… It is ‘ba’avur’ (because) of that the Eternal did for me when I came forth out of Egypt, is equivalent to the verse’s saying “such and such did G-d do unto me.” The word ba’avur also serves to indicate something within a subject itself, [and it does not only convey the idea: “because” of some other subject]. This is as the case in the verse, ‘ba’avur’ the child that was alive thou didst fast and weep, [which means “while” the child was alive], and not “because”. [David did not fast and weep “because” the child was alive; he fasted and wept “while” the child was alive so that it should get well.]
Rabbi Abraham ibn Ezra said that the purport of the verse is: “Because of that which I do and worship Him by eating the Passover-offering and the unleavened bread, the Eternal did for me wonders until He brought me forth out of Egypt.” But it is not correct. I will yet explain this verse.

בעבור זה, this was the reason G’d performed miracles for me so that I would subsequently perform this sacrificial service for Him. We find something analogous to this thought in Psalms 118,24 זה היום עשה ה' נגילה ונשמחה בו, “This is the day that the Lord has made, in order for us to exult and rejoice on it.”