- Question: If you aren’t sure if you recited the Birkas Hamazon why do you have to repeat the entire blessing but if you are unsure if you said Birkas HaTorah you should only say the second blessing of “Asher bachar banu”?
A. Both Birkas Hamazon and Birkas HaTorah are Torah level blessings and though the fifth paragraph of Birkas Hamazon is rabbinic it is said with the rest though by Birkas HaTorah only the second blessing is said to take care of the Torah level blessing because it is considered the better of the two blessings as the Mishna Berura 47:1:1 says.
B. Mishna Berura 184:13 says that the reason why you say the entire Birkas Hamazon including the last blessing paragraph is in order to not denigrate that last blessing and start to always skip it since it would not be taken seriously.
C. Birkas Hamazon is a blessing of praise and Birkas HaTorah is a blessing over a mitzvah.
Answer: Rav Moshe Feinstein (Igros Moshe Orach Chaim 2:3) says that a person would put the same weight of a blessing on a mitzvah as if it is a mitzvah and would never be lax in the matter and stop saying it but by bentching because it’s just a praise then the seemingly less important praises they would stop saying if skipped at times.