Parashas Metzora · Passuk 14:34
Chabad.org — English translation + Rashi
Torah Temima points to Sukkah 3b (verified on the daf).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “In a house” — it was taught: A house that does not contain four amos by four amos does not become tamei through negaim. Why? Because the word “house” is written concerning them.
Minimum size
Chazal require a minimum floor area of four amos by four amos before a structure is subject to the laws of house-negaim.