Reply To: Hilchos Shmiras Haloshon

The source for the above Halacha is “Sefer Chofetz Chaim”, B’eer Mayim Chaim, Hilchos Loshon Hora, klal 6, s”K 9. The Chofetz Chaim says there that if you don’t reprimand someone who is speaking L”H, it is as though you are the one speaking L”H.