Daf Yomi Insights - Berachos 9

The Shulchan Aruch (OC 477:1) mentions that one should be careful to eat the Afikomen before Chatzos. The Biur Halacha explains as follows:
The Gemara says that according to Rebbe Elzazar ben Azariah the Korban Pesach  could only be eaten until chatzos, midnight. Since matzo is juxtaposed in the pasuk to the korban it follows that one can only fulfill his obligation to eat matzo until chatzos as well. Rebbe Akiva disagrees and says that the Korban Pesach may be eaten all night and, consequently, matzo may also be eaten all night. The Rishonim differ as to whether the Halacha is in accordance with REB"A as there are many anonymous mishnayos that follow his opinion, or do we follow the opinion of Rebbe Akiva since the rule generally is that we follow Rebbe Akiva when he disagrees with one of his colleagues.
The Rambam, Magid Mishne, Baal haItur, Ohr Zarua in the name of Ri MiKorbil all hold that one can fulfill his obligation of matzo all night. Some say this is also the opinion of the Rif as he does not quote Rava's statement that according to REB"A one who eats matzo after midnight has not fulfilled his obligation. However, there are many of the leading rishonim who are of the opinion that one cannot fulfill his obligation after chatzos. They include Rabbeinu Chananel, the SMAG, Mordechai, Rabbeinu Yerucham and the Ohr Zarua leans that way as well, that one who eats after midnight has not fulfilled his obligation from the Torah.
The ROSH, Rokeach, Rashba and Ran are unsure and therefore say that it is best to be careful not delay the eating of matzo until after chatzos. Some Rishonim say that even Rebbe Akiva only meant that eating after chatzos fulfills one's Torah requirement, but he holds that in order to ensure that one does not transgress the mitzvah it is forbidden to intentionally delay until after midnight. The GRA says this also in his commentary. For this reason many Achronim concluded that even though one is certainly obligated to eat matzo even if he delayed until after chatzos, as the Halacha might be in accordance with Rebbe Akiva that one can fulfill his obligation all night, still if it is already after midnight and he is first eating matzo he should not recite the brocha of על אכילת מצה as when there is a doubt about reciting a brocha we do not recite it.