TT #192 · Parshas Shemini · Aliyah 7 · Passuk 33
Chabad.org — Vayikra Chapter 11 with Rashi
English: “Into its midst”: this excludes a bed, chair, bench, table, boat, and earthen lamp that have no interior cavity.
Toras Kohanim.
Wikisource — Sifra, Shemini, Chapter 7
Textual exclusion — The Chazal derives the stated rule directly from the wording of the verse.
Specified open earthenware objects are excluded.