Liturgy for Pesachim 10:4
מָזְגוּ לוֹ כוֹס שֵׁנִי, וְכָאן הַבֵּן שׁוֹאֵל אָבִיו, וְאִם אֵין דַּעַת בַּבֵּן, אָבִיו מְלַמְּדוֹ, מַה נִּשְׁתַּנָּה הַלַּיְלָה הַזֶּה מִכָּל הַלֵּילוֹת, שֶׁבְּכָל הַלֵּילוֹת אָנוּ אוֹכְלִין חָמֵץ וּמַצָּה, הַלַּיְלָה הַזֶּה כֻלּוֹ מַצָּה. שֶׁבְּכָל הַלֵּילוֹת אָנוּ אוֹכְלִין שְׁאָר יְרָקוֹת, הַלַּיְלָה הַזֶּה מָרוֹר. שֶׁבְּכָל הַלֵּילוֹת אָנוּ אוֹכְלִין בָּשָׂר צָלִי, שָׁלוּק, וּמְבֻשָּׁל, הַלַּיְלָה הַזֶּה כֻלּוֹ צָלִי. שֶׁבְּכָל הַלֵּילוֹת אָנוּ מַטְבִּילִין פַּעַם אַחַת, הַלַּיְלָה הַזֶּה שְׁתֵּי פְעָמִים. וּלְפִי דַעְתּוֹ שֶׁל בֵּן, אָבִיו מְלַמְּדוֹ. מַתְחִיל בִּגְנוּת וּמְסַיֵּם בְּשֶׁבַח, וְדוֹרֵשׁ מֵאֲרַמִּי אוֹבֵד אָבִי, עַד שֶׁיִּגְמֹר כֹּל הַפָּרָשָׁה כֻלָּהּ:
They poured the second cup for him. And here (kan) the son asks his father [In all of the texts it is not written "kan," but "ken," as in (Numbers 27:7): "Ken (Rightly) the daughters of Tzelafchad speak." That is, it is right that at the pouring of the second cup the son should ask:] "Why is this night different from all (other) nights? For on all nights, we eat chametz and matzah; this night, only matzah. For on all nights, we eat all greens; this night, maror. For on all nights we eat flesh roasted, boiled, and cooked; this night, only roasted." [The son would ask thus when the Temple was standing.] "For on all nights, we dip once; this night, twice." And according to the understanding of the son, his father teaches him. He begins with the obloquy ["From the beginning, our forefathers were idolators and we were slaves, etc."] and he ends with praise ["G d drew us close to His service and redeemed our fathers from Egypt."], and he expounds from "A wandering Aramean was my father" until he concludes the entire section.