A Chiddush in Halachah from the Sefes Emes

Based on the pasuk: ומשלוח מנות איש לרעהו – “Sending portions a man to his friend”, the Sefes Emes (Megillah 7b) writes, that one doesn’t fulfill the mitzvah of mishlo’ach manos by sending mishlo’ach manos to his Rav or Rosh Yeshiva because the mitzvah is to give, איש לרעהו, to a friend, to an equal, and it isn’t proper to call your rebbe, “my friend.” However, the Sefas Emes accedes that if a Rosh Yeshiva gives him mishlo’ach manos, this means the Rosh Yeshiva considers him an equal. So now he can reciprocate and send back mishlo’ach manos.