TT #195 · Parshas Shemini · Aliyah 7 · Passuk 33
Chabad.org — Vayikra Chapter 11 with Rashi
English: “Everything that is inside it”: the rule applies to what is within the vessel itself, not to what is within another vessel; a punctured vessel is excluded according to the verse’s condition.
Toras Kohanim.
Wikisource — Sifra, Shemini, Chapter 7
Textual limitation — The Chazal derives the stated rule directly from the wording of the verse.
The rule is limited to the vessel's own interior.