TT #110 · Parshas Shemini · Aliyah 5 · Passuk 8
Chabad.org — Vayikra Chapter 11 with Rashi
English: You shall not eat of their flesh, and you shall not touch their carcasses; they are impure for you.
Sifra (Toras Kohanim), Shemini, Chapter 3.
Sefaria — Sifra, Shemini, Chapter 3
טְמֵאִים. תַּנְיָא, טְמֵאִים – מְלַמֵּד שֶׁמִּצְטָרְפִין זֶה עִם זֶה.
Aggregation — The plural “impure” teaches that the prohibited animals can combine with one another for the relevant measure of impurity.
The plural טמאים teaches that the prohibited substances can combine for the relevant measure rather than being treated as wholly separate prohibitions.