Daf Yomi - Sukkah 25 - Oseik bemitzvah derabanan exempting mitvah medoraisa

Rav Elchonen in Kovetiz Shiurim 2:32 and the Sdei Chemed (maareches oseik page 436) discuss whether the principle of one being exempt from one mitzvah when engaged in another mitzvah applies when the mitzvah one is engaged in is derabannan and the other mitzvah awaiting him is deoraisa. The Sdei Chemed quotes the Rashba who writes that from our Gemara it is evident that one who is engaged in a mitzvah derabannan is exempt from a mitzvah deoraisa. The Mitzpei Aisan on Daf 10b wonders why one who is going to receive his teacher, which is only a mitzvah derabannan, should be exempt from dwelling in a Sukkah, which is a mitzvah deoraisa. The Mitzpei Aisan quotes a Ran in Shabbos who writes that a mitzvah derabannan does not override a mitzvah deoraisa even by saying sheiv vaal taaseh. Rather, a mitzvah deoraisa will override a mitzvah derabannan with sheiv vaal taaseh. Reb Dovid Goldberg here quotes the Bikkurei Yaakov who writes that receiving one’s teacher on Yom Tov is a mitzvah deoraisa of es HaShem Elokecha tira, which comes to include talmidei Chachamim.