Serpent Serpent, Open Your Mouth

Rashbi and his son seem to be sharply divided in the interpretation of the Mitzvah if Tzaraas appearing in the walls of one’s home.
Sources
Chumash Vayikra Perek 14 Pesukim 1 - 4
Rashi on Possuk 2
Gemara Bava Metzia 84 B
Gemara Sanhedrin 71 A
Likkutei Sichos Chelek 2 Devarim Page 359 Ois 3