The Talmud exegetically understands that when the Torah refers to Matzoh as Lechem Oni, "Oni Bread", this means "poor-man's bread." Accordingly, the Talmud rules that just as paupers eat their bread in small slices, one is required to eat Matzoh in slices, and not whole. Therefore, one is obligated to "break" one's loaf of Matzoh before eating it on the Seder-night(s) of Passover. Maimonides rules that one is supposed to break the Matzoh immediately before reciting the Matzoh, right before one eats it. However, Rabbi Asher ben Yechiel (1250-1328) rules that one is supposed to break the Matzoh even before, he says one should break the Matzoh before the recitation of the Haggadah. Rabbeinu Manoach asks on this Ashkenazic custom cited by Rabbi Asher ben Yechiel, why one should break the Matzoh before the recitation of the Haggadah if the requirement for the "poor man's bread" only says that one must eat the Matzoh in pieces, and at that point in the Seder one is not yet eating the Matzoh.
Rabbeinu Manoach himself answers that since in the beginning of the Haggadah, when one recites the invitational passage to the poor and hopeful prayer about the future, "Ha Lachma Anyo", one refers to Matzoh as "poor man's bread", then one is obligated to make the Matzoh into poor man's bread before saying this paragraph. Rabbi Betzalel HaKohen of Vilna, the author of Mareh Kohen on the Talmud, answers that the Talmud also learns from Lechem Oni that Matzoh is "bread over which many things are answered". Rashi explains that this means that the entire Haggadah is recited in front of the Matzoh. Therefore, explains Rabbi Betzalel HaCohen, these two laws in the Matzoh, of being poor-man's bread and of being present during the discussion of the Exodus, are supposed to be in effect at the same time. Consequently, one is obligated to break the Matzoh to make it into poor man's bread before he begins to use the Matzoh's presence to say the Haggadah, not just when he actually eats the Matzoh.
 Pesachim 115b
 Deuteronomy 16:3
 Laws of Leavened and Unleavened Bread, 8:6
 Abbreviated Hilchos Pesachim from Rabbeinu Asher (printed after the Rosh in the standard Vilna Shas)
 Rabbeinu Manoach on Maimonides' laws of Passover are printed in the Shabsai Frankel edition of Maimonides' works (Jerusalem).
 Cited in Talleli Oros Haggadah to Yachatz
 Pesachim 36a, 115b
 To Pesachim 36a