At the beginning of Magid, we say the paragraph of הא לחמא עניא, “This is the bread of affliction.” In this paragraph, we say the words כל דכפין ייתי ויכול, “All those who are hungry, let them come and eat.” This is a very nice gesture toward the poor, however it seems to be out of place. If this was an actual invitation, it should be made during the day or at Shul, not in the privacy of our own homes after the Seder has already started.
This invitation is just a further illustration of why Matza is called לחם עוני, “the bread of poverty.” In the time of the Bait Hamikdash, guests could not be invited in the middle of the Seder because the Korban Pesach could only be eaten with prearranged participants. The reason that we are permitted to invite guests to join our meal is because, in our spiritual poverty, we have no Korban Pesach. Therefore, our call for guests is to emphasize the fact that we are in exile.
There is another explanation as to why we invite the needy. Pesach recalls not only Hashem’s kindness to the Jewish People but also the kindness that Jews extend to their fellow Jews. The Chachamim tell us that the Jews merited redemption from Egypt because no Jew ever informed on another to the Egyptian authorities, no matter how cruel their persecution was. On the contrary, they made a pact among themselves to render kindness to each other. In turn, they merited the Divine kindness from Hashem that lead to their redemption. As we relive this special moment, we invite all people to join our celebration and share our blessing with them. This is the reason we begin our Seder with an act of benevolence.