Or HaChaim on Exodus 13:8/אור החיים על שמות י״ג:ח׳

1 והגדת לבנך, "you shall tell your son, etc." The expression והגדת instead of ואמרת is unusual and our sages in Shabbat 87 state that the term implies "words which are as tough as tendons." Another peculiarity is the expression ביום ההוא, "on that day," whereas immediately afterwards the verse concludes with the expression בעבור זה, "on account of this." The Haggadah shel Pessach as well as the Mechilta understand the verse as referring to a time when Matzah and bitter herbs are in front of you, i.e. at night. Seeing that I know that the time for that recital is at night, why did the Torah have to mention "on that day" at all? Furthermore, why do we need the word לאמור seeing that the Torah already wrote והגדת, "you shall tell?"

2We may have to understand all this in accordance with the statement in Pessachim 116 that when one recites the Passover story one begins with aspects which reflect discredit and concludes with aspects which reflect credit on the Jewish people. The discredit consists of the fact that our ancestors were pagans, something one can hardly boast about. The Torah therefore hints at this procedure by writing והגדת, "you will relate matters which are as tough as tendons;" you will conclude with אמירה, i.e. לאמור, words which recall that you were meritorious. The words ביום ההוא are a hint of the future redemption when the night will be called "day" (compare Psalms 139,13). It is also a reminder that the night preceding the morning of the Exodus was illuminated for the Jews (see our comment on 12,30). The Torah adds the words בעבור זה so that we will not err and conduct these ceremonies during the hours which belong to the day but at the time when we have to consume Matzah, i.e. in the evening. Possibly the words והגדת and ביום ההוא have been placed next to one another in order that we will also include the miraculous way in which that night turned into bright daylight for the Jews.

3Another reason that the Torah had to write the word לאמור in addition to והגדת is that the former was addressed to "your son." A father of girls or a husband not blessed with children might have concluded that since he had no son he would be free from the obligation to conduct the annual סדר celebration; the Torah writes לאמור, to tell us that even if the person is all alone he must relate what happened during that night to himself. Seeing that this is so, you may well ask why the Torah had to speak about a father telling his son at all? Perhaps I would not have known that under certain conditions one must "tell oneself" the Haggadah shel Pessach unless the Torah had used extra verbiage. Perhaps the Torah hinted that if someone is particular about telling of the Exodus, G'd will eventually grant him a son to whom he can relate these events.

4בעבור זה, "on account of this, etc." Perhaps the word זה (numerical value 12) alludes to 12 commandments connected with the Passover observance. The first three are the lamb, the unleavened bread, and the bitter herbs; then there is the Haggadah followed by the seven days of the festival and the benediction over wine on the night of the festival. The Torah has to phrase it as בעבור זה עשה because the seven days of the festival do not count as seven separate commandments in the list of 613 commandments.