Reference for Sanhedrin 110:6
ואם בא עליה אחד מכל העריות האמורות בתורה מומתין על ידה והיא פטורה
— R. Joseph said: Come andhear! <font>A maiden aged three years and a day may be acquired in marriage bycoition, and if her deceased husband's brother cohabits with her, she becomeshis.</font> The penalty of adultery may be incurred through her; [if a <i>niddah</i>] <font>shedefiles him who has connection with her, so that he in turn defiles thatupon which he lies, as a garment which has lain upon [a person afflictedwith gonorrhoea]</font>.<span class="x" onmousemove="('comment',' A man who had sexual connection with a niddah, defiles that upon which he lies even if he does not actually touch it. But the degree of uncleanliness it thereby acquires is not the same as that of bedding upon which a niddah herself, or a person afflicted with gonorrhoea, lies. For in the latter case, the defilement is so great that the bedding in turn renders any person or utensil with which it comes into contact unclean; whilst in the former, it can only defile foodstuffs and liquids. This is the same degree of uncleanliness possessed by a garment which has lain upon, or been borne by a zab (i.e., one afflicted with issue). ');"><sup>5</sup></span>