Halakhah for Yevamot 10:5

From the laws of this commandment is that which they, may their memory be blessed, said (Yevamot 5b, and see Mishneh Torah, Diverse Species 10:2) that there is only a prohibition from Torah writ of a combination of wool and flax if they are shua, tavui and noz. [This] is to say that the wool is shua by itself, meaning to say, beaten, and tavui (spun) by itself and noz by itself - and the explanation of noz is woven (see Rashi on Niddah 61b and Rabbenu Tam in Tosafot on Niddah 61b) - and so [too] is the flax shua, tavui and noz, by itself; and afterwards he combined them together - for example, he wove them, or even if he tied them one to another, once he tied two knots, this is shaatnez from Torah writ, for which there is lashing. But the whole time that these three [processes] that we have written are not done to them, it is not shaatnez from Torah writ, but [only] rabbinically, according to the opinion of some commentators, and we do not administer lashes for it. But it is forbidden rabbinically if one of the [processes] that we have mentioned - either shua or tavui or noz - is done to them. And this is what they, may their memory be blessed, said (Mishnah Kilayim 9:9), "the ones alone are forbidden" - meaning to say, rabbinically. And there are some commentators that said that [even] with one of these [processes], it is forbidden from Torah writ - and when they said about this, "forbidden," it is meaning to say from Torah writ.