Rashi on Numbers 5:13/רש"י על במדבר ה׳:י״ג

1ושכב 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).

2אתה 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)]

3תעלם מעיני אשה AND IT BE HID FROM THE EYES OF HER HUSBAND — Since it speaks of the eyes of the husband, it excludes the case of a blind man (i.e., a blind man cannot subject his wife to the ordeal). On the other hand, it states: “if it be concealed from his eyes”; it follows therefore that if he sees her improper conduct and wilfully closes his eyes to it the waters cannot try her (i.e., she cannot be subjected to the ordeal) (Sifrei Bamidbar 7:3; Sotah 27a).

4ונסתרה AND SHE WAS ASIDE SECRETLY with him such a period of time wherein there was a possibility for her to become defiled by intercourse (Sotah 4a).

5ועד אין בה AND THERE BE NO WITNESS AGAINST HER — But if there was even only one witness against her who stated that she was defiled she did not drink the מים המאררים, but was henceforth forbidden to her husband (Sotah 2b).

6ועד אין בה AND THERE WAS NO WITNESS AGAINST HER, as regards defilement, but there were witnesses regarding her meeting with the man privily.

7ונתפשה [AND SHE WAS NOT] SEIZED — i.e. subjected to force (Sifrei Bamidbar 7:3). Similar is, (Deuteronomy 22:28) “And seizes her (ותפשה) and lieth with her”.