I recently finished Meseches Makkos and went through the Agadetahs (Summed up very quickly) of when Raban Gamliel, Rabbi Elazar Ben Azaria, Rabbi Yehoshua and Rabbi Akiva were together and Rabbi Akiva laughed, while the other Tannaim cried whereupon Rabbi Akiva gives his reasons why he laughed.
I recall seeing a Noam Elimelech Al HaTorah where he discusses this Agaditah but I can't seem to find it. I believe its in the end of Sefer VaYikra or in the beginning of Bamidbar.
If someone knows where it is I would greatly appreciate it. Thanks