This episode addresses two difficult Tosfosim in Psachim (116a and 117b). The first says we shouldn’t say more than 7 languages of praise (in our intro to Hallel) corresponding to the seven heavens. The second says that the 39 melachos of Shabbos correspond to the 39 melachos that the Mitzrim made us do - after all, the word “parech” in at bash equals 39.