Parashas Terumah · Passuk 25:4
Yevamos 4b — the Gemara identifies techeiles as wool, deriving it from the fact that shesh is linen.
English: The school of Rabbi Yishmael teaches that the garments mentioned in the Torah are wool or linen, and the Torah commands techeiles. Since techeiles is wool, and “shesh” is linen, techeiles must be wool.
What Is Learned: The Gemara uses the materials named in the priestly garments to establish that techeiles is wool.