3,102. Which Combinations are Shaatnez?

Hilchos Kilayim 10:2

If a sheep is born to a goat, one is not liable for combining its wool with linen, though it is prohibited by rabbinic enactment because it gives the appearance of wrongdoing. If wool and linen are connected in any way, they are mixed fabrics under Biblical law. Therefore, if wool and linen were mixed or combed together and made into a smooth composite, they are considered mixed fabrics. If they were mixed and combed together and then a garment was made from this fabric, they are considered mixed fabrics.

Hilchos Kilayim 10:3

If someone sewed wool fabric to linen, even if he sewed them using silk, if he sewed a wool garment with linen thread or a linen garment with wool thread, if he tied wool threads with linen threads or braided them together, or even if he put wool and linen together in a sack or a basket and twisted them – in all of these cases, they are considered mixed fabrics. Even if he tied braids of wool and of linen together with a leather strap between them, they are considered mixed fabrics. The same is true if he folded wool and linen fabric together and tied them. This is all because the Torah says “wool and linen together” (Deut. 22:11). They are prohibited by virtue of being combined, regardless of the manner.