In the beginning of this week’s parshah the Torah writes about Avraham Avinu’s famous act of hachnasas orchim for the three men who were passing by his tent. The first pasuk in the parshah reads, “Vayeira eilav Hashem – And Hashem appeared to [Avraham].” The Gemara (Baba Metzia 86b) states that Hashem had come to visit Avraham Avinu who was still healing from performing his bris mila. Nonetheless, despite Hashem’s presence, Avraham Avinu went to perform hachnasas orchim. The Gemara (Shabbos 127a) says that we learn from this story that the hachnasas orchim is greater than kabalas p’nei haShechinah (greeting the Shechina)!
However several Achronim ask: Since Avraham was in the middle of performing the mitzvah of kabalas p’nei haShechinah, why did he stop and perform another mitzvah? There is a rule that osek b’mitzvah patur min ha’mitzvah (when someone is doing one mitzvah he is exempt from doing another). So even if the mitzvah of hachnasas orchim is greater than kabalas p’nei haShechinah, Avraham should have been exempt from its performance since he was in middle of performing another mitzvah. The question is even stronger according to the opinion of the Ritva (found in his commentary on Sukkah 25) that one who is performing one mitzvah is not allowed to perform another mitzvah.
Some suggest that we can answer this question based on the opinion of the Nesivos Hamishpat (72:19). The Nesivos says that the general rule of osek b’mitzvah patur min ha’mitzvah only applies when one is performing an obligatory mitzvah. When a person is performing a non-obligatory mitzvah, he may perform another mitzvah if he so wishes. So even though Avraham was performing the mitzvah kabalas p’nei haShechinah, he was allowed to perform the mitzvah of hachnasas orchim and did so because this mitzvah is greater than the mitzvah of kabalas p’nei haShechinah.
I am not sure, though, why the mitzvah of kabalas p’nei haShechinah is considered non-obligatory. I would assume that if Hashem appeared to someone, he would be obligated to remain in Hashem’s presence for as long as Hashem remained.
In fact, there is a halacha that one must greet his Rebbe (mekabel pnei rabo). The Gemara (Rosh Hashanah 16b) says that on Yom Tov one is obligated to mekabel pnei rabo. The Magen Avraham (Orach Chayim 301:7) says that it is an obligation on Yom Tov and a non-obligatory mitzvah on Shabbos and Rosh Chodesh. In siman 554 the Magen Avraham cites an opinion that it is an obligatory mitzvah on Shabbos, Rosh Chodesh, and Yom Tov and a non-obligatory mitzvah every day of the week. So if one is obligated to greet his rebbe at least on certain occasions, I think it is logical that there is a similar obligation to greet the Shechina.
Be that as it may, I believe we can answer the question in another manner. Perhaps the reason one who is performing another mitzvah is exempt from performing another mitzvah is because who is to say that the second mitzvah is greater than the first? And it wouldn’t make sense to leave a greater mitzvah for a smaller one. It’s true that the Gemara tells us that hachnasas orchim is greater than kabalas p’nei haShechinah, but there may be circumstances when doing a smaller mitzvah is greater (e.g., lefum tzara agra – the more the effort the more the reward). Therefore, we have a general rule that osek b’mitzvah patur min ha’mitzvah. Why, then, did Avraham stop performing the mitzvah of kabalas p’nei haShechinah to perform the mitzvah of hachnasas orchim? Because in his situation, he understood the mitzvah of hachnasas orchim to be greater than kabalas p’nei haShechinah.
