Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos) By the Chofetz Chaim

This book lists the Torah mitzvos that can be observed today

Second Section – the Negative Commandments

181. It is negative commandment “do not wear a garment with wool and linen”

As it states in Devarim (Deuteronomy) 22:11, “do not wear shaatnez, a material mixed with wool and linen together.” This is called a Kilaya of clothing. Wool specifically means it is from a sheep or a ram. Once wool and linen are combined together in this world, they are forbidden by Torah law. If a person wears this mixture, even if it is only occasionally or even if it is on top of ten other garments and he does not benefit from it at all or even if it is only to get past customs inspection, he has transgressed this negative commandment. Also, a person who covers himself with a mixture from wool and linen has transgressed this commandment. According to the law of the Sages, it is forbidden to sit on mats made of this mixture, even if ten mats are placed above it to soften it and the bottom one is made of this mixture.

This applies in all places and at all times, for men and for women.