פּירוש אויף במדבר 5:13

ושכב איש AND A MAN LIETH [WITH HER] — a man, thus excluding a minor and a being that does not come under the term איש (i. e., an animal) (Sifrei Bamidbar 7:2; Sotah 24a).

ושכב איש אותה, and another man has lain with her It is characteristic of the evil urge to cause the sinner to proceed from a relatively mild sin to ever more serious sins.

ועד אין בה, to testify that she had been guilty of adultery,

אתה שכבת זרע [AND A MAN LIETH] WITH HER CARNALLY — This implies: that only her sexual intercourse with another man makes her unfit for continuing in marital relation with her husband, but the fact that her sister had sexual intercourse with him does not make her unfit for such (Yevamot 95a) [as was once the case with two sisters who greatly resembled each other (Tanchuma 5:2:6)]