Kommentar zu Bamidbar 5:28

ואם לא נטמאה האשה AND IF THE WOMAN WAS NOT DEFILED on the occasion of this secluding herself with this man,

ונקתה, from the penalty that would apply for causing a needless oath. In this instance, G’d, Who knows the true circumstances, will certainly not consider this oath as having been a frivolous one.

לא נטמאה האשה וטהורה היא ואם, And if the woman had not been defiled and remained pure, etc. The reason the Torah repeats that the woman had remained pure is that the Torah wishes to tell us that not only has she become exonerated so that the waters will not harm her, but she shall even conceive seed. The additional word וטהורה also indicates that not only had the woman in question not been guilty of intercourse with someone other than her husband, but she had not indulged in any of the caressing and fondling which usually precedes sexual intimacy. When both these conditions exist she will be blessed by becoming pregnant in accordance with what the Torah writes. If, on the other hand, לא נטמאה, she had not become defiled through actual intercourse but could not claim to be "pure" by not having indulged in foreplay, she will not be blessed with child although she will escape punishment for her conduct.