The "Or Sameach" (Chapter 7 of the Laws of Chametz and Matzah, Halacha 4) infers this from the language of the Rambam, who wrote: "And he should expound on 'Arami...' etc., and whoever adds and elaborates on the exposition of this section is praiseworthy." At first glance, it is difficult to understand from where he derives that it is appropriate to add and elaborate on the exposition of this section. The "Or Sameach" explains based on what is stated in Pesachim (36a): "And Rabbi Akiva, the reason we read 'poverty' (in 'lechem oni' – bread of poverty) is like Shmuel said: 'Lechem oni' – bread over which many things are answered." Why is there a need for answering (response) of words, since the mitzvah of "And you shall tell your son" is explicitly stated, and the recitation of Hallel on the night of the Seder is rabbinic? Rather, the intention is to expound on the section of the Bikkurim (first fruits), where the term "answering" is written, 'And you shall answer and say before the Lord your God,' and this is the intention of answering many things, that one should elaborate on the exposition of this section. This is the essence of his words. It is clarified that whoever increases in telling (the story) is meant to expound on the section of Bikkurim, whose entire purpose is to inform that one is not ungrateful (Deuteronomy 26:3 in Rashi), and to give thanks for the abundant kindness and goodness.